A few set-up questions!
With everything as it has been these past few months, I've had more time to start going on local nature walks and in the process become fascinated with our native fish species. I'm in the planning stages of a native biotope tank, and the thought of constructing it as a paludarium is very tempting, to reflect the shallow shoreline habitat of the species I've seen in the wild. The intended design is primarily about the habitat for the fish and aquatic inverts, the emersed area will just be for marginal and bog plants. I plan to set it up in a 29g I have lying around, with the idea that if all goes well, I'll upgrade to a 30 or 40 breeder to have much nicer dimensions for a shallow pond shoreline!
There's a few things I've had a hard time uncovering in my research though, so I was hoping I could get some clarification and advice from others who have set up these types of tank before!
Firstly, I'm not a fan of the setup where the land is suspended over the water, which wouldn't be representative of the shoreline anyway. I'd also really prefer not to have to silicone in any barriers. I've seen a few tanks which I like, which seem to use rocks or driftwood to build up a sort of wall to retain the slope, and I think this would suit well. My questions here are - if I use crushed lava rock or some of those fired clay balls like in hydroponics to be a "drainage" layer and keep the soil substrate above the water table, do I need to worry about that area going stagnant or trapping lots of mulm? I've seen some setups line the rocky wall area with filter floss to keep the soil trapped, and I'm not sure if again that would lead to issues of trapped decaying matter? (Or even shrimp getting stuck back there!)
My second question is about filtration. I am hoping to keep and breed ghost shrimp in the setup, as well as various freshwater copepods. Is there any kind of filter that would be alright with the free floating larval stage of the ghost shrimp, other than a sponge filter? Alternatively I am considering a small canister filter with an intake guard, but I am not sure if that would be enough to protect the shrimp larvae.
I'm even wondering if I could get away with no filter, as the species I'm interested in keeping come from very slow moving or even stagnant water. Of course this would require more water changes and lower stocking, but I wonder if a Walstad-esque setup would work there. I plan to use hornwort primarily, as that is the species found where these fish live, and I'm not sure if that would be sufficiently planted to allow me to go filterless. My preference is to have water circulation, I'm just not sure if it's feasible with the inverts I want to keep.
Thanks very much in advance!