HannahJ
Aquarium Advice Activist
I'm kinda late to the topic, but here's some advice I don't think has been said yet.
Do not use a chemical pH buffer! I can not stress that enough. Whoever sold you yours may have meant well, but it will end up doing more harm than good. There are natural pH stabilizers you can utilize if you absolutely need to (coral/limestone/bubblers in the tank to raie the pH, peat/CO2 to lower it, etc), but you are really best just letting your pH be. Your fish will stand it just fine.
On using both AmQuel and NovAqua--NovAqua is a water conditioner. You want to be using it, it will remove chlorine and chloramines from your water. And yes, you can use it instantly, I do on all of my fish tanks every water change. However, I would recommend you stop using AmQuel. If you notice, it purports to remove Ammonia, which should not be necessary at all in a cycled tank. In fact, by removing the ammonia from the tank when you use it, it is in a sense starving some of your nitrifying bacteria, which could be part of your problem. You can use just NovAqua without using AmQuel, and your tank will be better for it.
Also, one very important thing for you to consider: you said you were using a test kit that involves strips--throw it out. Strip testing is wildly innaccurate, which could be the source of a lot of these inconsistent test results, rather than actual changes in your pH. Go and buy a liquid test kit (the recommended brand on this forum is AP Freshwater Test Kit), it is well worth the money, and will be a thousand times more accurate.
Another thing, do not be afraid to do as many PWC's as is possible. PWC's are never bad, and can be done daily with no ill effect, so long as you condition the water and match the tank temperature. You should be doing, at the least, a PWC once every other week, with once a week strongly recommended, especially in a slightly overloaded tank like yours. The exact amount of water you need to change isn't set in stone. I usually do about a 1/3 PWC every week, but you might need a 50% PWC.
The best way to find out how much you should change is to look at your nitrAtes. You want your nitrAtes to be under 40ppm at a bare minimum, and anyone on this forum will tell you that under 20ppm is really best. If your tank tests at 50ppm on nitrAtes, then a 50% PWC will put them at 25ppm. While you probably shouldn't do more than a 50% PWC at a time unless you are really in danger, I would recommend doing a 50% PWC daily until your nitrAtes are under 20ppm, and then just doing once a week PWC's (though be sure to monitor your water parameters). To make these water changes easier, you might look into getting a Python vacuum. They hook into your sink so the bucket/jugs of water thing isn't needed anymore.
Also, if your water is cloudy after a PWC, this is likely because stuff on the bottom of your tank is getting stirred up into the water. Try giving your tank a really good vacuum/cleaning and see if that helps.
Another thing I noticed is that you are using a Millenium 1000 filter. I believe those are only marked for use up to 15 gallons. It moves about 90 gph and you really need at minimun 5 gph per gallon in your tank (with over-filtering recommended in tanks like yours where it might be a little overcrowded). In a 20 gallon, you'll want a filter with at least 100 gph turnover, and maybe a bit more. You might look into getting a new filter. If you do, though, be sure to run it on your tank with the old filter for a while to build up bacteria on it, before removing the old filter. And you can skip filters that rely mainly on charcoal or carbon--that sort of mechanical filtration is good for very little. You want a filter that rather offers mechanical filtration and has a lot of good surfaces for bacteria to grow on.
Sorry for the long post. I hope all of this has helped some. Good luck!
Do not use a chemical pH buffer! I can not stress that enough. Whoever sold you yours may have meant well, but it will end up doing more harm than good. There are natural pH stabilizers you can utilize if you absolutely need to (coral/limestone/bubblers in the tank to raie the pH, peat/CO2 to lower it, etc), but you are really best just letting your pH be. Your fish will stand it just fine.
On using both AmQuel and NovAqua--NovAqua is a water conditioner. You want to be using it, it will remove chlorine and chloramines from your water. And yes, you can use it instantly, I do on all of my fish tanks every water change. However, I would recommend you stop using AmQuel. If you notice, it purports to remove Ammonia, which should not be necessary at all in a cycled tank. In fact, by removing the ammonia from the tank when you use it, it is in a sense starving some of your nitrifying bacteria, which could be part of your problem. You can use just NovAqua without using AmQuel, and your tank will be better for it.
Also, one very important thing for you to consider: you said you were using a test kit that involves strips--throw it out. Strip testing is wildly innaccurate, which could be the source of a lot of these inconsistent test results, rather than actual changes in your pH. Go and buy a liquid test kit (the recommended brand on this forum is AP Freshwater Test Kit), it is well worth the money, and will be a thousand times more accurate.
Another thing, do not be afraid to do as many PWC's as is possible. PWC's are never bad, and can be done daily with no ill effect, so long as you condition the water and match the tank temperature. You should be doing, at the least, a PWC once every other week, with once a week strongly recommended, especially in a slightly overloaded tank like yours. The exact amount of water you need to change isn't set in stone. I usually do about a 1/3 PWC every week, but you might need a 50% PWC.
The best way to find out how much you should change is to look at your nitrAtes. You want your nitrAtes to be under 40ppm at a bare minimum, and anyone on this forum will tell you that under 20ppm is really best. If your tank tests at 50ppm on nitrAtes, then a 50% PWC will put them at 25ppm. While you probably shouldn't do more than a 50% PWC at a time unless you are really in danger, I would recommend doing a 50% PWC daily until your nitrAtes are under 20ppm, and then just doing once a week PWC's (though be sure to monitor your water parameters). To make these water changes easier, you might look into getting a Python vacuum. They hook into your sink so the bucket/jugs of water thing isn't needed anymore.
Also, if your water is cloudy after a PWC, this is likely because stuff on the bottom of your tank is getting stirred up into the water. Try giving your tank a really good vacuum/cleaning and see if that helps.
Another thing I noticed is that you are using a Millenium 1000 filter. I believe those are only marked for use up to 15 gallons. It moves about 90 gph and you really need at minimun 5 gph per gallon in your tank (with over-filtering recommended in tanks like yours where it might be a little overcrowded). In a 20 gallon, you'll want a filter with at least 100 gph turnover, and maybe a bit more. You might look into getting a new filter. If you do, though, be sure to run it on your tank with the old filter for a while to build up bacteria on it, before removing the old filter. And you can skip filters that rely mainly on charcoal or carbon--that sort of mechanical filtration is good for very little. You want a filter that rather offers mechanical filtration and has a lot of good surfaces for bacteria to grow on.
Sorry for the long post. I hope all of this has helped some. Good luck!