I have a betta in a 2.5 gallon tank with a sponge filter and a few live plants. When I put the plants in the pH was around 7.0-7.2, but I tested it again today (a few days later) and it was 7.6+. I read online it could be because the plants are using up the C02 in the water and doing so increases the pH.
Is this true? And if so how should I maintain a low pH? I've seen those DIY kits around but I'm not sure how feasible that is for small tanks like mine. Any recommendations?