API root tabs and leaking into water colomn???

[AllenIsbell]

I feel that the root tabs won't do you any good considering your substrate literally has water flowing through it. Dirt, sand, or even a finer gravel would be able to store the nutrients for the roots. You might as well go with a liquid fertilizer.

My .02

[Bolsen27]

If you completely cover them they will not leak. They leaked on me because I buried my bubble wand too close to a few of them which ended up making a mess. As soon as I corrected that the problem went way.

[Cermet]

Your ammonia spike is not good - adding tabs should not do that unless you have a lot of waste food and other organics in the substrate; yes, plant food can help bacteria - esp. phosphates. Even if the substrtae was clean, the tabs will quickly dump most of their nutrients into the water column and encourage algae growth - without a proper substrate, tabs are not very useful.

As bethyMT said, why not add sand to fill between the rocks? Of course, you'd have to clean the substrate well before adding the sand (some) to fill between the gaps.

I'm lost how such large rocks aid your plants - most streams, even very rocky ones - have finer gravel/sand as fill between and this forms a VERY hard, dense structure. That might be an issue for your system unless you use very little sand.

Plants do need finer gravel/sand to hold their roots allowing nutrients to be held as well. Tabs are not meant to be used to fill the water column so not really a good idea to use them in that manner.

You can get around the problem with your current substrate by one of two routes: remove all the larger rock pieces and clean very carefully between the smaller ones every few days; or do this once every few months but do large water changes very often (every few days.) Either case, you need high effort to maintain that type of substrate.