I just set this up Saturday afternoon with the intention of following the Walstad method. It's a 46G bowfront tank with about 15 species of flora and no fauna as of yet - I want to get the plants established before I cycle the tank for fish. I used organic potting soil as the base layer and then used about 3/8-1/2 inch of black sand as the cap. I used less than the recommended inch of gravel as Walstad recommended using less - she writes that sand could "suffocate" the soil so less is needed.
As you can see, a lot of the sand cap has gotten shifted around or worked into the soil. Did I not use enough? Is it worth it to rip it up and redo the substrate now, while it's still new? Or can I just leave it? Should I add more sand, or at this point use gravel or something completely different?
I would drain the tank, remove the plants, add a full inch of sand or fine gravel, and replant/refill the tank. If you don't you may have difficulty ever getting clear water. I would also make sure that if all of the sand/gravel settles into the lower areas there will still be sand/gravel over all of the soil in the higher areas.
You may be able to add a bit more of the cap without draining and dismantling the tank. You'll want to be careful not to bury the plants, but someone used to post a vid of using a plastic soda/water bottle to add substrate to a full tank. Most of the cloudiness remained in the bottle.
The set up looks nice, it should look great once the plants grow in.
I don't think there's any reason why you cant get the plants established and start cycling the tank at the same time. If nothing else, you could start at a lower ppm, and gradually ramp it up to the recommended level (3-5ish) as the biofiltration gets established.
Thanks for the advice! I've had someone else recommend draining the water and just adding more substrate - not removing the plants. I'm pretty excited by the bottle method to add substrate to a full tank, though - but I guess if there's ever a time to rip it all up, it's now.
You really don't need a cap at all. I have a couple mud bottom tanks with no cap and they haven't given me any problems. And as someone else stated you can add a cap without draining the tank. Prerinse the cap material and just pour it in cup by cup - I find doing this in a filled tank acutally help distribute the cap evenly around plants.