So here is the freshwater dirt-planted 40 gallon breeder tank approaching the end of the first year in operation. I couldn’t be happier…well if the fish would quit eating all the plants, that’d be great. But other than that. 😀
This type of setup is known as a “Walstad method tank” as it uses a dirt substrate capped with gravel rather than a complex system of filtration. In this method, all of the filtration is done with the plants absorbing the stuff that the fish leave off, giving back oxygen into the water.
In the “pure” method, that is all that is done other than water top offs for evaporation.

I have modified this slightly. I use a hang on back filter to get detritus (bits of floating plant debris and general gunk) using filter floss only. There is no chemical filtration involved. I also added a 515 gph water pump to give circulation and a bit of current. In addition to evaporation top offs, I also do bi-monthly 30%-40% water change to get rid of the tannin leaching (orange colored water) that occurs with dirt + mopani wood.
Compared to the maintenance that a standard freshwater fish tank requires, this is almost no work at all.
The white specks you can see in the video is the end of the feeding session. Today it was brine shrimp. Fish go wild for brine shrimp. heh.
The two black sailfin mollies are a mated pair, and you can see some of their offspring toward the end of the video.
The tuxedo Platys are mated somehow (not sure…maybe a new age triad?) and they have offspring as well.
The big gourami is a favorite of mine and is happy to be hand fed.
Off to the fish store for a few more plants tomorrow. This gang love eating the plants, and I’ve lost about 1/2 of the “verge” at this point. I think of it as snack food for when I’m not about.