I have wanted to write this review many times but talked myself out of it each time until now, when I was using up the rest of this order of tabs. I have used hundreds of these root tabs and each time has been a frustrating experience. It is ridiculously difficult to keep these buried in your substrate. I have tried using these in standard heavy aquarium gravel, eco-complete, sand, and a combo of these together and have had the same experience: they will not stay buried, even in a 3.5-4” deep substrate bed.
They will either immediately float up or you will come back to your tank 5-10 minutes later to find root tabs sitting on the surface of your substrate or worse, floating at the top of the tank (which gives you the fun job of trying to figure out where you now have to re-add tabs).
The coop has said that the fertilizer in the root tab shouldn’t be harmful to anything living in the tank or cause issues with water quality which is good. It does kind of defeat the purpose though when root tabs are supposed to add fertilizer to the substrate, not the water column.
Also, once they are in the water for a few minutes you aren’t really able to push them back into the gravel because they disintegrate when touched. Cory has given “tips” on how to solve this problem by using a needle to poke a hole in each root tab to squeeze the air out but that is an annoying solution to the user, especially when they are trying to use 100+ of them at once.
When they stay in the substrate they work great but their finickiness makes them not worthwhile even with how much of a bargain they are. They are very hard to recommend to the point that I actually dissuade others from buying them which is unfortunate because they do fertilize plants very well. This is a coop product I unfortunately can’t get behind.