Growing Plants Emersed On Top Of An Aquarium In An Acrylic Tray

The clay balls are a fired expanded clay, very porous like lava rock. I’ve used clay in a hydroponic veggie garden in a flood/drain setup and the balls do float until waterlogged. Not an issue if you have constant flow. You can also use pea gravel, rock wool, lava rock, etc, just something inert. Coco coir also works well, but not appropriate for fish unless you’re doing a black water biotope. Sand might be a little too fine but don’t see why it wouldn’t work either with proper screening to keep it out of the overflow. No need to use fancy substrates.

The premise is the water carries all the nutrients so no soil is needed other than to just anchor the plants and hold in the moisture for the roots. If you look at nft systems the water depth needed is minimal, less than 1/4 inch. you just need the plant roots to reach it ok and that you have a reasonable flow rate for nutrient transport. I’d aim for maybe an inch or Less. Then add more for the “dry” layer to fill in the depth you need so the top isn’t wet and anchors the plants well. I also used seedlings in net pots and rock wool, no substrate in the tray itself and water just high enough to touch the wool. Many ways to do it.

I think the simplest way would be a small pump running constantly from the tank to one end of the tray, and an overflow on the other side going back to the tank. Height of the overflow determines depth. I’m using essentially the same configuration with a timer and an extra hole drilled to accomplish a flood/drain cycle.

For ferts standard ei style is fine I would think. With atmospheric co2 available, it may take more than you’re used to. Something fish safe.

Keep us posted.