I've been researching if a pool filter sand cap will work for the Walstad method. I read that if one uses a 1" layer of sand it will suffocate the soil, but I'm afraid if i use less than some fish, like my ram will displace some of the sand and make a mess. I dont want to use gravel because I'm not sure fine plants like monte carlo can grow in it (can it?). I monte carlo can grow in gracel than I will use that. What do you you all suggest I do?

Thanks in advance.

Using pool filter sand as a cap is a pretty common practice. If you get true pool filter sand that is #20 sized grain, it won't make a mess in the tank, and it won't "suffocate" the soil as the grains are large enough for water to seep in. You will have to rinse it several times to get a good portion of the dust off of the sand but after that, it does a really great job.

Aqua Quartz® 50lbs Pool Filter Sand (61308) - Pool Maintenance Equipment - Ace Hardware

I'm sure there are more experienced folks that will chime in on this.

Thanks, how thick of a cap do you recommend for my particular situation?

1" of pool filter sand should suffice.

So just to clarify, 1" of pool filter sand won't be to thick?

1" is just about right. I wouldn't go any deeper.