Fishless cycling

Originally posted by TCLynx on AGC, June 4, 2010

Here is the basic of fishless cycling in a nutshell so to speak.

Dose system to an ammonia level between 1 and 2 ppm
then wait and test till ammonia levels start dropping.
If the ammonia levels drop below 1 ppm and the nitrite level is still below 1 ppm, then dose again.
If ammonia or nitrite levels are still high then wait and keep testing.

Eventually both ammonia and nitrite levels will drop.
Then dose to 1 ppm again and see how long it takes for both ammonia and nitrite levels to reach 0 again.
Once you get to the point where you can dose to 1 ppm and have both ammonia and nitrite drop to 0 within 24 hours, then the system is fishlessly cycled.

If you are going to get fish early, then quit dosing. You don’t want to put new fish into a system when the ammonia or nitrite levels are high. Add salt and extra air.

There have been reports that the bacteria that convert ammonia to nitrite establish quickest at a higher ppm than 1 or 2 of ammonia. Like I think I once heard 5 ppm. So perhaps for a first dose, bringing the ammonia up to around 5 ppm might do some good. However, I’ve never cycled that way and I’ve also read that high ammonia levels will inhibit the next phase of the nitrogen cycle until the ammonia levels drop, by which time one is likely to have nitrite levels off the chart. I managed to cycle a system fairly quickly during cool weather using the dose up to 1-2 ppm method.

So what ammonia source do you use and how much do you use? Well I can only really comment on what I know personally. I use humonia or Pee if you will. I generally put it in an old water bottle and seal it up for a couple weeks before use. Aging the urine allows the urea content to convert to ammonia. This does two things, 1- it kills off most e. coli that teds to get into urine from our own skin and 2- the already converted ammonia makes dosing easier without the risk of overdosing that is common with fresh pee. People will often pee in a system and then test the next day and see no ammonia and figure more pee was needed and so pee again, and again and again then suddenly the ammonia levels spike and just keep climbing off the charts as more and more of the urea is changing into ammonia. Basically there is a delay with fresh urine.

I found that About one pee worth a day will be more than enough to cycle a system. For my barrel ponics system I usually dosed with about 200 ml of aged urine but I didn’t need to dose every day. Let the test kit be your guide. For my big system which had about 600 gallons of fish tank at the time of fishless cycling, I used between 200 and 500 ml per dose and again, I did not dose daily, only as the test kit indicated I should.

If you are going to use a non pee ponic ammonia source. Please make sure you get pure ammonia that has not other additives like fragrance, or soap, or detergent that could have the effect of killing fish/bacteria when they get into the system. I personally don’t know of any safe sources of such an ammonia product to recommend.
I have also heard of people using urea fertilizer to dose a system, warning urea is gonna take time to convert to ammonia, it is kinda like using fresh pee. Over dosing is common with urea for cycling. See if you can find someone who has used it to recommend how much should be used. Fish emulsion will also break down into an ammonia source but again, it will take time. I guess anything high in protein that will rot can become an ammonia source but I kinda recommend against putting lots of rotten stuff into an aquaponic system that is new as it is difficult to tell what sort of negative things you might also be introducing, it would be difficult to measure and the smell might be nasty.

Fishless cycling is less stressful than putting new fish into a new system and then having to test and watch and restrain ones self from feeding the hungry beggars. If you miss a day of testing during fishless cycling, no worries, there are no fish in there to be killed. If you overdose, generally the worst that can happen is you need to wait longer or perhaps do a bit of a water change. If algae gets going, no worries there are no fish to suffer from it, just cover the tank. If something goes wrong with the plumbing in a new system while it is fishless cycling, well now you know what needs fixing before you get fish. See, far less stress.

38 comments to Fishless cycling

  • Hi, I am not sure if your article Fishless cycling | Aquaponic Lynx LLC is the right place to put this but I have placed a link to your blog on my page. I think my page is somewhat relevant to yours so maybe you can piggyback a little of my traffic.
    Regards, Norah Sultani

    PS. It is on the right sidebar on my page. Maybe you can put a link back?

  • […] have done posts about fishless cycling so I’ll let you go read that if you choose the less stressful […]

  • I’ve got a newly started system. i have tried the cycling with pure ammonia, but after about 3-4 weeks all i have is very high nitrite levels. what shouled i do to get this to change over to nitrates. larry

    • TCLynx

      Have patience. Perhaps reduce your ammonia dosing a bit if you haven’t already. The bacteria that convert nitrite to nitrate are the slowest ones to colonize and if you are still dosing large amounts of ammonia you might be inhibiting them a bit as well. Anyway, the nitrite spike is often the hardest part to get past and if temperatures are cool it can seem to take forever but the truth is, you are only at about week 4 right? Cycling often takes 6 weeks under good conditions if you don’t have some mature media to start the system off with. So patience is the best bet. Keep an eye on your system pH since I’ve often noticed a sudden pH drop about the same time the nitrites drop rapidly.

  • Hi there,

    I’m doing fishless cycling with a bathtub system. I have high Nitrates, but also very high Nitrites still.
    Because the nitrites are bad for the fish I don’t want to put them in there until it is down.

    Will it go down over time or should I add salt?

    Also the PH is really high at like 7.6 so I will adjust that as well. Maybe when I do that the nitrites will go down?
    Ammonia I’m keeping at about 2ppm at this point, was at 4ppm before the nitrates appeared.

    The plants seem to be happy, but you can tell that the lettuce is lacking nitrogen or something.

    Thank you!

  • TCLynx

    I would hold off adding fish until after the nitrite goes down.
    Adding salt will not help the nitrite go down any faster, salt is only to help mitigate the nitrite toxicity to the fish but since you don’t have any fish in there yet it isn’t needed.
    (Though 1 ppt of salt would be nice for the fish when you first get them just as a general tonic.)

    A pH of 7.6 is not that bad and it will naturally come down as the system gets cycled up and the buffer gets used up. Be ready to buffer the pH back up a bit since as the system finishes cycling up it is not uncommon for the pH to drop and if it gets below 6, the bacteria can slow or even stall out.

    I would actually recommend seeing if you can dose the ammonia and then wait 24 hours then do water tests to see where the ammonia, nitrite and nitrate are 24 hours after dosing the ammonia. Once you get to the point where ammonia and nitrite are both 0, 24 hours after a dose, then you can count yourself as cycled up and you will be ready for fish.

    The lettuce is probably not lacking for nitrogen if you say your nitrates are high. More likely you are lacking for something like potassium or other trace elements. You might add a small dose of seaweed extract and see if that helps your lettuce.

    Have patience with a new aquaponics system, don’t go changing too many things at once, let the system cycle up and settle in before you expect too much from it.

  • Joe Bifano

    I have 2 systems.
    The first one looks like it is cycled because when I put in Ammonia 24 hours later it is 0. The nitrite and nitrate is also 0. Should I have some nitrate readings on this side? There are no plants on this side and I thought for sure that I should have nitrates. I am confused.

    The other side does the same thing, the Ammonia is 0 or close to it in 24 hours. But the nitrite is high about 5 and the nitrate is about 5 to 10. I stopped feeding this side ammonia today and I am waiting for this to come down. You called this the nitrite spike. I am not sure why the nitrates are high on this side and not the other. I have some plants on this side on a shelf system like you made so they only get an hour to 2 on watering. They are doing bad. Stopped growing and turning yellow, brown and purple. I am on the aquaponics community forum and you have helped me there.

    • TCLynx

      Hi Joe, I think I need more information to give better answers.
      You say you add ammonia and then it is 0 24 hours later. how much do you add? as in say an hour and a half after you add the ammonia what is the ppm? I recommend dosing enough ammonia that after the ammonia distributes and mixes around the whole system you get to between 1-2 ppm. Cause if it is a big system and you just add a little ammonia, it might be too dilute to even read once mixed.

      On the other system yes, nitrite spike and that lasts longer. Yes holding off on dosing the ammonia for a few days till the nitrite falls is a good call. Once the nitrite falls, dose the ammonia again to between 1-2 ppm then check back the next day to see if both ammonia and nitrite are 0 in 24 hours. Getting to the both at 0 in 24 hours may take a couple weeks even.

      Which system is it you say the plants are not looking good? I’m gonna guess you are maybe having nutrient deficiencies and/or nutrient lock out due to pH. What is the pH? You may also be experiencing some nutrient deficiencies because pure ammonia only provides for nitrogen and no other nutrients. Plants could be seeing many deficiencies and most people take care of potassium and trace elements with some seaweed extract. I have also been experimenting with some gro tone fish emulsion fertilizer for use in fishless systems and I’ve even tested it in components that have become systems with fish and so far no harm to the fish as long as you don’t go spiking your ammonia and nitrite with fish in the system.

      • Joe

        It has been 3 hours since I dossed it and I should have checked sooner. I am at .5 on Ammonia so should I add more to get it too 1-2ppm?

        The system that has the nitrite spike is where the plants are right now not the one I just tested above. The PH is 7.6 on the low test and on the high it is 8.0

        I used Maxcrop seaweed powder to help with some trace elements. I had the post on the forum on purple tomatoes and everything has stopped growing. I am considering getting the plants into some rafts to see if that helps them. What do you think about getting them into the rafts?

        I also have 2 pees that have been sitting for over 2 weeks and could use this when the nitrite goes down not sure?

        • TCLynx

          The pH is high and that is likely to be causing a huge amount of your slow growth on the plants.

          I’m not really an expert at telling what is best to do about the purple plants but maybe using the hummonia for your next dose would be appropriate after the nitrite spike is past.

          A bit of patience is in order here. It is a brand new system and a huge number of greedy plants are not always the best choice in a brand spanking new system. No, I don’t think moving them to a raft would be any better for them, I’ve actually experienced even more deficiencies under poor nutrient availability in a raft.

  • Joe

    I added enough to get it to 2ppm after waiting 1.5 hours. The nitrite and nitrate are both at 0.
    Is that okay?
    Will I see any Nitrate?

    If I test again in 24 hours and the ammonia is at 0 then it is cycled.

    The other side I just tested and it is at 0 on everything so I want to add pee. I have 2500 gallons about how much would you add?

    Both sides have been cycling for a while and I did put in Nitrafying bacteria to kick start this.

    • TCLynx

      On Side A, where you added ammonia and it’s at 2 ppm. If both ammonia and nitrite are 0 tomorrow then perhaps it is cycled. If that is the case I have to wonder where the nitrate is going. Is there any algae in the system, if so that could be using up the ammonia even before it gets converted.

      Side B. How much pee to use, I’m not sure since it will vary from person to person but 2500 gallons is pretty big. On systems between 300-900 gallons I never used more than about a pint per dose. How much aged pee do you have on hand? I might guess about 4 pints? But that is really guessing because I don’t know the strength of it.

  • Joe

    On Side A there is Algae, not a lot but still there is on the sides of the rafts. I have 2 large sweetwater air blowers going and I am at 60 degrees with DO at 8. I am also at almost 6000 feet elevation near Denver. The fish tanks are covered and the rafts are in with no holes.
    Is there a way to get rid of all algae before I put in the fish?

    Side B today was above 0 but not 5 so there was some nitrate. There is very little algae on that side. So this makes sense now. I will dose it like normal then on this side and see how it goes.

    • TCLynx

      Block all light from the water is the only good way I know to get rid of algae.

    • Joe

      The low nitrate could also be caused by a product I used called AmmoniaFix. I saw it in the store and thought that it would add the correct bacteria but reading it again it says that it eliminates ammonia/nitrite/nitrate. If this is the case and the algae is not using the nitrate but the AmmoniaFix is, what should I do? Is there a way to add nitrate safely until the system starts working like it should? Could this be why my plants stopped growing? There are only 8 10×20 trays with seedlings that have completely stopped.

      • TCLynx

        I have no personal experience with AmmoniaFix. I’m guessing it does what it does by some how chemically locking up ammonia and I have no idea how that affects cycling and the bacteria and the plants long term.
        I’m not sure what to tell you at this point since you have done something I have no experience with.

  • Joe

    Yesterday I tested 2 times and I was back to having a high nitrite level at 2ppm and nitrate was back up to 10 on the B side. So the AmmoniaFix is not taking out the Nitrate. I called the company and they said that it would only take out Nitrate in the anaerobic areas. I dosed at 5:oo Thursday the last reading at 3:30 because I had to leave. Just now it was 0 so I will dose again and get a reading in 1-1/2 hours and again in 24 hours.

    The A side was at .25 on nitrite and 2 on nitrate not quite 24 hours so I tested again just now and I am at 0. I will dose this side and wait the 24 hours as well.

    It should be getting there soon I hope.

  • Joe Bifano

    Hi TC,

    Had several days of 24 hour dosing going to 0 so today I got 300 catfish. About 5 -6 inches for .70 each. I hope that was a decent cost. I wanted to know after the initial shock of the new environment when should I feed them and how often and how much?

    • TCLynx

      WOW, that is a large number of fish to start off with. Good Luck with it. Now you did once mention 2500 gallons. Is that 2500 gallons of fish tank or is that total amount of water in the system? And do you have enough filtration to handle max stocking of that amount of water? You mentioned trays but that doesn’t really tell me what your filtration is. For flood and drain media bed systems growing out channel catfish, (once they get past the fingerling quarantine stage) I like to put them in a tank with 10 gallons per fish and I usually have twenty gallons of gravel filtering for each fish. So basically I’m saying I have a 2:1 ratio grow bed to fish tank system. I have twice as much volume of media based plant bed as I have fish tank. I do tend to grow the catfish large. With bluegill I tend to stock far more fish, Like about three times as many since bluegill usually only get grown out to about a third or a half a pound while my catfish usually reach 3+ pounds in the first year and if I keep any longer they can easily top 6, 8, or even 10 pounds. But you have to have adequate filtration and aeration to get them big without mishaps. If the water quality starts to deteriorate, they get sick.

  • Joe Bifano

    I have 2 separate systems 1 is 3000 total gallons with a 1200 gallon fish tank and 1500 gallons in rafts that are 2- 24’x4′ and the rest in media based beds 2- 4’x4’x1.5′ 2-1’x10’x1′ and 1 4’x8’x6″. The other side is 3300 total gallons with a few larger items but almost the same. I am putting 150 fish in each so it is not as many as you thought. I had another post on the forum and we were at 125 to 150 fish in our calculations for each side. I went with the count because I thought that I would loose some from the trip. I have about 5 to 10 in each tank that are struggling and will see if they make it. Plus I am going to add a 4’x8′ media bed to each side right away that was not in the calculations. I will also be looking at adding more rafts if needed. I have 2 large sweetwater air pumps and have been over 8 to 9 on DO and I am at 6,000 feet elevation here. I also have a friend that will take 50 from me next week if this is to many. Does this sound better?

    • TCLynx

      Keep a close eye on your ammonia and nitrite levels and adjust feed if either spike. Start eating some fish once some of them get up close to a pound to reduce numbers so as you get fish getting close to 3 lb, hopefully you will only have 1 fish for each 10 gallons of fish tank and keep eating fish so as you start to get really big fish you are reducing the numbers.

      Once numbers get rather low, you will want to finish harvesting one of the tanks completely so that you will have that system ready to take you next supply of fish (you will have to decide if 100 fish will be enough or if you are going to want to continue to stock more heavily.) Anyway, hopefully you will work it out so you can stagger your stocking from one system to the other so perhaps one summer you stock one side and the next year you stock the other.

      I would probably recommend salting the system to between 1-2 ppt of salt to protect from any nitrite spikes you might get and to also help sooth the skin and improve slime coat. The light salt tonic can help against infection that often comes from stress and handling. Don’t salt heavily for catfish though since they do have sensitive skin 3 ppt is the max I’ll ever salt mine to again and only if they are showing signs of disease, otherwise I just salt to 1-2 ppt when getting new fish or when I will be netting them for transport.

      Beware, channel catfish are scardy cats and excessive use of nets in the tank tends to stress them out as well as causing injuries that can become infected and kill fish. NEVER net you catfish just to show to people. And I now have a rule that I won’t go netting fish more than once a week. As in if you want me to harvest fish today, make sure you have me net out as many as you will want for the next week or so since I won’t allow them to be disturbed again for a week. I found that if I netted them one day and then netted some more say two days later, I usually found at least one dead fish a few days after that. I haven’t had that problem since I implemented the one week rule.

      If I know I’m going to be handling a lot of fish (like maybe for moving them) I might mix up a salt water and aloe dip for the net to hopefully sooth and protect any scrapes the net does cause on the fish. It seemed to work last time I did it. Just have to have a bin large enough to dip the net in with the solution between each scoop into the tank.

  • Dreen

    Hi there,

    I have a new system, with tilapia growing up a bit in a separate tank. It is a mixed system with 1/2 media beds and half rafts. I added humonia at the beginning of fishless cycling, and the ammonia is at 4.0 after two weeks. Nitrites are off the charts. I am aerating and is a flood and drain CHOP system. How long should I wait for the ammonia to go down? It’s been running for 3 weeks and is at 4.0 now. I do have some plants in, and many seeds started, but the roots aren’t yet really going for it, if you will. I was planning on putting the fish in the IBC in two weeks. I’ve also been adding the wash out from the fish filters and the water changes from keeping the fish in the brooding aquarium. Should I change half the water? Or should I just wait another week before I do anything?

    More info…The temp on the tank in the system is having a tough time getting and staying over 70. The PH is high, we have a lot of limestone here. 7.6 or higher. I haven’t bothered to check the nitrates yet, but nitrites are pegged out along with ammonia.

    • TCLynx

      Cycling with or without fish takes time. It looks like you WAY over dosed with ammonia which could be slowing things down a bit so a partial water change and perhaps adding a little phosphoric acid might help get things moving a little more, or you might just wait it out. However you probably should not plan on adding fish till you see the nitrite drop below 1 ppm. Be sure to quit adding any more ammonia till you see the ammonia and nitrite drop significantly and once you add fish don’t add any more ammonia.

      Under Ideal conditions cycling usually takes at least 6 weeks (those people who talk about cycling in 3 or 4 weeks are talking about just getting past the initial ammonia spike and that is only under ideal conditions.)
      With the temperatures low, you are not under ideal conditions.

  • Dreen

    I also added Maxisol, so that may have have helped send it off the charts. I’ll change out half of the water and then isolate the water in the tank to get it closer to 80 before I bring it into circulating through the beds.

    I’ll check the levels after a half change out and see how it’s going. Should I consider the start to be dependent upon the results after changing out half of the water? In other words, looking at six weeks from the change out?

    Thanks so much. You and your site are very helpful!

    • TCLynx

      I don’t know what Maxisol is so I don’t know if it had anything that would contribute to the ammonia or not. Maxicrop Original doesn’t really affect ammonia if used in reasonable quantities.
      I expect the cycling process has started since you have nitrites. You might want to check your nitrate levels but since we don’t know the starting nitrate levels it might not tell you a whole lot.
      As for as when the six weeks starts. At this point it simply takes as long as it takes. Test your water regularly. When you see the ammonia and nitrite levels drop make sure to watch your pH as well since it sometimes drops drastically then too depending on the amount of buffering capacity your water has.
      When both ammonia and nitrite are below 1 ppm you can consider adding fish sometime after that. I like to wait until ammonia is 0 and nitrite is only a trace before adding fish but I usually also like to be able to dose to 1 ppm of ammonia and have both ammonia and nitrite down to 0 within 24 hours before I consider it completely fishlessly cycled.

  • Dreen

    Changed out a bit mre than half the water and it is still reading 4.0 on ammonia. I added a quarter cup of muriatic acid and will check all the levels again tomorrow. The tank was running for a half hour before I checked the ammonia.

    • TCLynx

      The suggestion about the phosphoric acid wasn’t really to lower the pH but more for providing some phosphorus since I’ve heard about complete lack of phosphorus stalling cycling in some cases. But with humonia that probably isn’t the cause of the issue. More likely it is just that the ammonia is just so high that the bacteria that convert the nitrite are just having difficulty getting going.

  • Dreen

    I said Maxisol from reading too many Aussie posts about Seasol! Sorry. It was indeed MaxiCrop. Changed out half of the water again and while it wasn’t running I added 140 gallons of hot water from the house. Gave me a chance to clean up more lava rock dust in the tanks…Won’t be doing that again! And hauling all that water was fun, too. LOL. Anyway, I’m going to wait until I am stable and have the right balance on nitrates and ammonia without swings to add the fish. I have four raft beds for lettuces and some herbs and four media beds, so hopefully those will develop the proper bacteria and get rolling along. I’m not that worried about the ph as I know it will come down in time, just about getting the bacterial colonies going well and keeping the temps, ammonia, and nitrites in the proper balance. Thanks!

  • Dreen

    So here are my numbers this morning. I think we’re heading in the right direction:

    Temp 74.6•
    PH 7.6
    Ammonia 2.0
    Nitrites .25
    Nitrates 5.0

    Maybe I am overly optimistic, but if I can get the temps up to 80 or so, I will feel like the bacteria are getting established. Also, the ammonia should come down, and obviously, the nitrification process looks like it is kicking in.

    Now for my question, I am aerating, but haven’t yet found a method to actually check the levels of DO. Do you have any recommendations?

    • TCLynx

      On a home/backyard scale, there are no really easy/accurate AND inexpensive methods to closely monitor DO. There are test kits out there. The really simple/inexpensive ones are probably not accurate enough to be of any real use. The better ones are going to be more expensive and a bit harder to use. For those really feeling that they need to monitor DO a meter is likely the way to go but they are costly and also require maintenance and proper calibration and use.
      If you are able to keep water quality good and you have aeration plus plenty of water circulation and you avoid having the water still during really hot weather, chances are your tilapia will be fine. I will remind that having aeration and pumps off for a while during HOT weather can spell disaster for any type of fish since very warm water can’t hold much oxygen to start with so it can be depleted quickly if a circuit trips or you forget to turn something back on after turning it off for some reason.

  • This is a happy day! Ammonia, is zero, nitrites are zero and nitrates are between 2 and 5. Ph is still 7,6 and has remained unchanged since the initial fill of the system. Don’t worry, I am not considering day 36 to be completely cycled. I will begin adding ammonia to the system in small quantities of 1 to 2ppm and see how the conversion rates go. I just wanted to thank you for your wonderful help and let you know that things are headed in a positive direction!

    • TCLynx

      Yep I always considered it to be “cycled” when you can add to 1 ppm of ammonia and have both ammonia and nitrite down to 0 ppm in 24 hours.

  • ZAB

    i am doing the fish-less cycle and my nitrites are zero and nitrates are 0 but my ph is low what do i need to do?

    • TCLynx

      I need much more information in order to help you cycle up.
      How big is the system and what type is it?
      How long have you been fishless cycing?
      What is your Ammonia level?
      What is the pH?
      What are you using as your ammonia source?
      How long has it been since you last dosed with ammonia?

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