[lildark185]

Is it possible to make your own nutrient rich substrate? What if a porous gravel were allowed to soak in some seachem iron and evaporated? Would this create an iron rich substrate that would last long enough or would it leak into the water column upon addition of water to the tank?

 

[MatPat]

I have tried something similar with Soilmaster Select and loaded it with macros. I'm pretty sure it leaches back into the water column but it would be an easy thing to test. Try adding some of Seachem's iron to your porous rock and allow it to evaporate. Fill up the container with some RO or distilled water and see if you can test any iron. Iron can be hard to test for so you may want to try it with a nitrate or phosphate solution if you have those around. If any shows up in the water in your container, you know it is leaching out of the rock

 

[Dryn]

I would be curious as to the validity of such an approach as most of the time, iron bonds to other minerals and becomes unusable to the plants. Alternatively, you can buy some cheap fired-clay aquatic soil at most pond stores, the home depot here sell it for about $5, and mix it in with the gravel. Kinda ugly though. I've used plain old potting soil made for cacti and palms that was supposed to be very "loose" underneath gravel, with the theory that it wouldn't stagnate. I got tired of the tank after about six months, but I had absolutely no problems and no algae blooms or nutrient spikes. It didn't smell or anything when I took it out. I did get some really funky stuff growing out of it, namely two different aquatic worms, a bunch of niterite snails and some cool stringy-looking bladderworts. This may not me the norm though, I am just trying to help.

 

[AaronT]

You could try the mineralized topsoil that I wrote an article about. It's essentially a means of making your own substrate that will last for many years to come.