I have 2 tanks. Tank A is 5 gallon bow front with aqueon 5 filter 50 watt heater. gravel for substrate, non planted. inhabitant is one male betta. tank has been active for 3 months. receives two 50% water changes per week with stress coat+ added. Filter has carbon removed replaced with sponge for biological filter. Tank B is rectangular 5.5 gallon tank with marine i25 filter 50 watt heater and gravel. also non planted and inhabitant is 1 female betta. tank has been active for 3 months. receives two 50% water changes per week with stress coat+ added. filter has carbon removed and replaced with sponge for biological filter.
Here is my issue: I tested the water tonight using api liquid tests.
Tank A: 0.25 ppm ammonia
Tank B: 0 ppm ammonia
Tank A: 7.8 ph
Tank B: 7.4 ph
both read 0 for nitrites and 5-10 for nitrates.
How can these two tanks which are basically the same and have the exact same water source have 2 different ammonia and ph readings???