It's a neat little project, but is it worth doing ?
I ask because I'm currently 3 weeks into an experiment keeping Bettas in 2.5 G tanks without filters, air stones or water changes either.
Each tank has one Betta. Each also has lots of Hygro difformis, anubias, and a couple of different mosses, along with a large almond leaf and a few oak leaves, on bare bottoms. I've tested regularly and so far, Ammonia 0, Nitrite 0, Nitrate < 10. Only top ups for evaporation. No 'cycling' of any kind was done on the tanks, they used to get twice weekly WCs and had no plants. After I put some plants in, I noticed the fish seemed to like it and eventually thought to test the water. I was surprised to find those results and they have been consistent ever since.
Fish are fine, they get fed about every second day, mostly live food that won't die if they take awhile to find it. At the rate we're going I'm thinking I won't have to do WCs more than once every 4-6 weeks, though I plan to keep testing for awhile yet.
For light, they have an 8 inch round clamp lamp on top, right on the tank rim, with a 6500 K spiral bulb, I forget if they are 9 or 11 watts, which keep the plants in great shape, growing well. They are on timers, 12/12, and no algae issues at all, it's been 12/12 for months now.
Because I'm growing out some mosses, I add 3 drops of API 'liquid carbon' every other day and one drop of Flourish once or twice a week, but they could easily do without that if I were content with slower growth. The tanks also have a very few MTS snails, not more than 3 or so, and I don't allow babies to stay in when I find them. I trim the difformis when it hits the top and leave the tops and leaves to root. Some I'll sell, some I'll replant. They are slightly weighted to keep the stems from floating up. I cut the usual plant weights into very tiny pieces, just enough to stop the stem rising, not enough to do any damage to the stem.
The fish seem to enjoy their quarters. They were all adopted after recovering from fin rot, and all appear to be regrowing the fins, to some degree at least. It is far less effort to keep them this way and I never have to worry that their water is going bad and I haven't changed it yet.
