I have a drop checker for my nano tank. At the moment the checker is basically yellow so CO2 is pretty high but the fish are not showing any signs of CO2 poisoning. They don't gasp at the surface and they swim normally like they did before I added CO2. Is there actually any point in me keeping the drop checker in there since it basically isn't telling me anything? Is there a problem with having more than 30/35ppm of CO2 as long as the fish are doing well? Thanks!