I remove half the water with a siphon, using it like a vacuum to clean the floor of the tank. You can use a length of flexible tubing. I refill the tank with temperature-matched, pre-conditioned water.
I do this once a week with a cycled 2.5g tank. If I were you, I'd do it at least twice a week, maybe more depending on how clean you keep the tank between changes.
I have a regulare size gravel vaccume that I use for my 40 and 50 gallon tanks,
Could I just use the tubing from that?
Although I think I tried it once but could'nt get it to start. How would I start the siphoning with the tube?
I have three tanks running on 3is and have been for over 6 months. Tanks are crystal clear and ammonia levels at 0. I do a 25 - 50% water change weekly. The work fine but are annoying as the connections loosen from the air pressure and the flow stops. I have to tighten everything at least once a week
I had that thing for awhile for my 5 gallon and honestly I hated it. My boyfriend got me a "quietflow" filter and I'm SOOO much happier with it. The best to "filter" the water in a 2.5 gallon is to just to daily water changes 20-25% (once a day). Be careful with what you put as substrate on the bottom, whenever I had gravel, it trapped SOOOO much gunk in it x_x