I'd like to do Flourite but it would literally tear heck out of things to go that way.
The tank bottom is 24" X 72". There's about 200 pounds of gravel/substrate in it now. There are only a few small areas of exposed gravel. Everywhere else, there are plants.
That's why I was wanting to use something I could "inject" into the existing substrate. I know that's going to be a lot of injecting! But I'd planned to do it a little area at a time during water changes... Starting with areas around the heavy root feeders. (Which are beginning to look unhappy.)
Dupla sells pre-made laterite balls that you can press into the substrate by hand. But... they want a small fortune for it. To make it affordable, I think I'm going to have to buy in bulk and make my own. Time consuming, but MUCH less expensive.
To give you an idea of the nutrient consumption... The tank has CF lighting @ 4.8 WPG and about 40ppm CO2. I'm adding 10 ml of Yamato Green-N concentrate (regular Yamato Green + Nitrate) every day. When I test the water in the morning, before adding the Yamato, iron reads zero and nitrate is usually between 0 and 1.5 ppm (virtually zero). I've started adding a capful of flourish-iron as well. So far, the plants are still sucking all of it up each day. I'm guessing that these are indications that everyone is getting almost all of their nutrition from the water column... and could use more since algae growth is minimal.
Plant species that can feed through the leaves are thriving. For example, I throw away/give away a 1/2 trash can full of hygrophila difformis every couple of weeks to keep it in check. However, root feeders are beginning to look puny.
In addition to the laterite, I had planned to either use some Jobes fragments and/or make some PMDD+clay pellets and place them around the root feeders.
This tank grew swords and other root feeders like crazy for a long time, but it appears that they have finally sucked up everything they can find.
Is my diagnosis reasonable? Is my remedy reasonable?