Understanding the Details

I recently read a post some where that was criticizing how advice in a public forum might get taken as gospel and run people into aquaponics disaster.

I can understand where this might come into play when one skim reads without doing much of the introductory reading and picking bits of knowledge from here and there without necessarily understanding the underlying details of any one method.

An example might be some one who reads part of a discussion where some one is given the advise to add some shell grit to their aquaponics system to keep the pH from dropping too low since shell grit is a buffer that will slowly dissolve and won’t raise the pH above a certain point so is some what self regulating.  Unfortunately, it seems some one skim reading that discussion without much underlying aquaponics education might mistakenly take from it the following…

Use shell grit to control pH

Shell grit will not lower pH, it will not control pH, it can buffer pH up.

Well if that person were starting up a new system with high pH tap water and they added a huge amount of shell grit or limestone into their media beds thinking it would control their pH to the proper value they would be wrong and some will blame the advise of the forum. Generally though that would not have been the advise of the forum. They didn’t tell some one to use shell grit to control pH, they said to use shell grit to buffer the pH so it wouldn’t drop too low and it is important to add the grit in small amounts or better yet, in such a way that it can be removed if it is buffering too much. Shell grit is slow acting so small amounts should be added long before the pH drops below the danger zone. I have a mesh bag of grit hanging in my fish tank. If the pH starts dropping lower than I like, I know it is time to add more grit or clean the bag or place it so more water flows through it. If I add to much I can pull the bag out for a day or two. This does not automatically make the pH the level we want it. All methods of pH adjustment require regular pH testing. There are no buffers that will automatically keep a system at a pH of 6.8. Buffers will not bring the pH down. Buffers buffer UP. Lime and limestone will generally cause a pH up over 8. Shells may be gentler and only take the pH up to 7.6 but that is still higher than most people like for growing veggies.

So, some will suggest that one should use other methods of adjusting pH and I suppose if one has a system with a very measured amount of water and feed input and wants to be able to calculate an exact amount of something to add each week or few days to keep a constant pH level, then perhaps they are right. However, shell grit can be used as a slow acting buffer for keeping system pH from dropping too low provided it is used in such a manner that one can control it.

Basically, don’t do what I did and fill your grow beds with shells or limestone. Your media should not be your buffer since you can’t control what is buried in your grow bed.

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