I increased my number of bettas to a total of 6. I spotted some nice looking fish. I'd been to the Petco three time and could see they were getting worse looking each time (see my post about Gossamer is much better since leaving Petco as an example) So it wasn't well planned. I could afford 5 gallon tanks they are $10 at a store where I live but finding enough surfaces for that many tanks without window or heating vents around was a problem. So I bought 2 gallon jars.(also $10.00) They are the right height ect. It's temporary I am buying 20 gallon to divide in a week. I still will have to wait for it to cycle though.
I really got to what difference it makes between a 2 gallon and 5 gallon.
Amonia spikes fast, the PH gets low and at least one fish tank had medium high nitrates (lavendar color). Based on what I see water changes probably need to be done at least 3x weekly. These are even sponge filtered. They keep the water clear looking but that seems to be it. I don't see the huge chemistry changes like that with a 5 gallon tank.
If you haven't tested your water frequently and you have a small tank check it out! I am really happy with all my fish but I will be very busy for awhile changing lots of water. I think I shoulda found a way to do lots of 5 gallons.