I'm new to this forum so apologies if I put this post in the wrong thread. I have this reoccurring problem where the soil in the tank gives off too much co2. The tank has been established w the soil for a little over a month maybe 2 months. The plants are fine but I'm worried about my fish. I have 4 longfin leopard danios and their gills are noticeably red. I was online looking at photos of these fish to differentiate their sex and I noticed the fish gills in the photos weren't nearly as red as the fish in my tank. Ammonia: 0 ppm / Nitrate: 5.0 ppm / pH: 7.6 / Ideas?
Would the fish show signs of stress if H2SO4 was present?
Lets go back to the beginning if we can. The tank has been established for only a month or two total? Or this is an older established tank that you added a soil substrate to only a month or two ago?
You say the problem is reoccurring. When did it start? How often/frequently do you notice it? What is it exactly that you're noticing other than the red gills?
What makes you think the soil is giving off co2? Do you see something to make you think that or are you just guessing? Are you seeing bubbles coming out of the substrate? If so chances are it is not co2. Doesnt necessarily mean you're seeing hydrogen sulfide but it could eventually turn into that and what you're seeing now is just excess "gasses". A lot of people find it useful to take something like a chopstick to poke around in a dirt substrate. This helps release those excess gasses so they dont build up and eventually turn into a giant cloud of hydrogen sulfide. It also helps pockets of anaerobic substrate from forming; which you want to avoid.
I'm not sure what stress a fish might display from h2so4. However, red gills is almost always a sign of either ammonia or chlorine poisoning in fish. I see those test results in that photo but cant make it out too well. I'm tempted to say if that first tube is your ammonia test that it looks a bit green to me which would indicate more than 0; but the photo isnt too great so I cant say that for sure.