coldcazzie
Ice Queen
Do you put a dechlorinator into the water when you do a water change? Tap water has heavy metals, chlorine and chloramine in it which are toxic to fish and the bacteria in your filter: a good water conditioner like Seachem Prime or Stress Coat will detoxify the heavy metals and remove the chlorine/chloramine so that it doesn't harm your fish.
Good that you don't replace the filter media - you should continue to just clean it in old fish water
About the pH - I had a similar question when I joined the forum 2 years ago. Is it my pH that's killing the fish. Answer, maybe, but the likelihood is that the pH being low is indiciative of a different issue: usually OTS or low KH, or both. Basically, nitrate is acidic. Your tap water has minerals in it which bind with the acidic organic substances, but if there is low mineral content (soft water) then that buffering capacity runs out quicker than if you have high mineral content (hard water). So if your pH is dropping very low very quick it is often a side effect of having soft water (I have soft water, as do quite a few forum members). The way to help it is to do weekly water changes and make them larger rather than smaller. So I do 50% a week rather than 25-30% a week which I might do if I lived in a harder water area. This is where OTS (old tank syndrome) comes in. If you don't do the water changes, your organic substance levels rise, pH drops...etc. Now I'm not saying that you've obviously not done water changes for several months, but I do think that perhaps monthly water changes are insufficient in your case.
If I were in your position (which I was, a couple of years back) I would do more frequent water changes at first: spend a month doing weekly water changes and see how your test readings come back. I would also buy fewer fish at a time (ie, about 6 at a time), and acclimate them by drip syphon over the course of 2-3 hours.
(Ps. actually pH 5 is not a problem for tetras/angels etc which come from south america, as the water there can naturally be as low as pH 4. However, it could be a problem for the livebearers, as you said, I think they prefer harder, more alkaline water.)
Good that you don't replace the filter media - you should continue to just clean it in old fish water
About the pH - I had a similar question when I joined the forum 2 years ago. Is it my pH that's killing the fish. Answer, maybe, but the likelihood is that the pH being low is indiciative of a different issue: usually OTS or low KH, or both. Basically, nitrate is acidic. Your tap water has minerals in it which bind with the acidic organic substances, but if there is low mineral content (soft water) then that buffering capacity runs out quicker than if you have high mineral content (hard water). So if your pH is dropping very low very quick it is often a side effect of having soft water (I have soft water, as do quite a few forum members). The way to help it is to do weekly water changes and make them larger rather than smaller. So I do 50% a week rather than 25-30% a week which I might do if I lived in a harder water area. This is where OTS (old tank syndrome) comes in. If you don't do the water changes, your organic substance levels rise, pH drops...etc. Now I'm not saying that you've obviously not done water changes for several months, but I do think that perhaps monthly water changes are insufficient in your case.
If I were in your position (which I was, a couple of years back) I would do more frequent water changes at first: spend a month doing weekly water changes and see how your test readings come back. I would also buy fewer fish at a time (ie, about 6 at a time), and acclimate them by drip syphon over the course of 2-3 hours.
(Ps. actually pH 5 is not a problem for tetras/angels etc which come from south america, as the water there can naturally be as low as pH 4. However, it could be a problem for the livebearers, as you said, I think they prefer harder, more alkaline water.)
