I think most other problems have already been addressed, but I do see one issue.
Are you adding tapwater and then adding buffer and trying to change the pH/kH/gH?
Bad Bad idea.
While it's more work and takes up more room, you need to get a large holding tank or tub if possible. You need to adjust your pH, kH and gH in THERE, NOT in your tank. Adjusting these parameters in the tank while other factors (namely the ammonia and co2 from the fish) are effecting them is 1. an exercise in futility 2. very frustrating 3. VERY stressful to your fish.
Not sure if I missed it or not, but when did you start having these problems? Did you grow the fish to a large size in the tank or just add them in? How long have they been there? Have you ALWAYS had problems with buffering (in which case you should have already been adjusting your tapwater accordingly before you added any fish to the tank), or did this just appear as the fish grew adding more bioload to your tank.
From what it looks like reading the thread the fish were added before the tank was ever cycled?
Also, a 300g seems a bit small for your fish load but shouldn't be causing problems THAT bad, so are you SURE it is 300g? What are the dimensions? I only ask because I see people that think they have a certain size tank but when dimensions are added up it's actually much smaller.
I also agree with whoever said you need to get your ammonia and other factors under control BEFORE you start messing with your parameters. You need to be watching very very closely and keeping it below .25 until you are fully cycled. It sounds to me like you're letting it get really high and it is causing a pH crash. You do a water change, the pH stablizes and then the ammonia immediately builds up again and crashes your pH. You may have to do multiple water changes per day EVERY day until the tank cycles.
I have cycled with large loads before and it is hard work especially with such a large tank, but unless you do the water changes and get the tank under control it will be an endless cycle of ammonia buildup, pH crashes killing whatever biobacteria that may have been forming over and over again. High ammonia also inhibits biobacteria growth which will not help.
Perhaps I missed it, but what exactly IS your ammonia and nitrites?
Are you adding tapwater and then adding buffer and trying to change the pH/kH/gH?
Bad Bad idea.
While it's more work and takes up more room, you need to get a large holding tank or tub if possible. You need to adjust your pH, kH and gH in THERE, NOT in your tank. Adjusting these parameters in the tank while other factors (namely the ammonia and co2 from the fish) are effecting them is 1. an exercise in futility 2. very frustrating 3. VERY stressful to your fish.
Not sure if I missed it or not, but when did you start having these problems? Did you grow the fish to a large size in the tank or just add them in? How long have they been there? Have you ALWAYS had problems with buffering (in which case you should have already been adjusting your tapwater accordingly before you added any fish to the tank), or did this just appear as the fish grew adding more bioload to your tank.
From what it looks like reading the thread the fish were added before the tank was ever cycled?
Also, a 300g seems a bit small for your fish load but shouldn't be causing problems THAT bad, so are you SURE it is 300g? What are the dimensions? I only ask because I see people that think they have a certain size tank but when dimensions are added up it's actually much smaller.
I also agree with whoever said you need to get your ammonia and other factors under control BEFORE you start messing with your parameters. You need to be watching very very closely and keeping it below .25 until you are fully cycled. It sounds to me like you're letting it get really high and it is causing a pH crash. You do a water change, the pH stablizes and then the ammonia immediately builds up again and crashes your pH. You may have to do multiple water changes per day EVERY day until the tank cycles.
I have cycled with large loads before and it is hard work especially with such a large tank, but unless you do the water changes and get the tank under control it will be an endless cycle of ammonia buildup, pH crashes killing whatever biobacteria that may have been forming over and over again. High ammonia also inhibits biobacteria growth which will not help.
Perhaps I missed it, but what exactly IS your ammonia and nitrites?
