python cleaner

Add your dechlor either just before refilling the tank, or pour it in the stream as it is going in the tank.

If you put dechlorinator in the water and that isn't a problem the pH is what is going to be deadly to your fish (if the change is over about .5+ or even less). If you are totally empting the tank, then you cannot just refill the tank either, you will have to go through a cycle. The filter and gravel will have bacteria cultures but the water will not, and therefore in a few days will go thorough a spike, and hurt/kill your fish. It will not take as long as a start up cycle but it will need to happen. You shold not perform a complete water change without cycling your tank.

Actually, there are very few ammonia- or nitrite-oxidizers in the water itself. They are almost entirely contained on the surfaces in the tank, esp. in the filter.

If the replacement water is similar to the existing tank water, in terms of pH, KH, GH and temperature, you can do large scale water changes without harming your fish or your biofilter. I regularly do 80% water changes on many of my Rift Lake tanks.

If your tap water and tank water differ, let us know by how much (and on which parameters) and we can help you figure out how much water could safely be changed at one time.

HTH,
Jim

The issue that I am talking about though is the change in the water perameters and the lack of bacterial cuture. with that much increase in water volume the density of the bacteria colony to the water is very low, and can cause a spike in your nitrites (nitrates if you are lucky). Thus making it a very in hospitable environment for fish to live in. If you are going to do a 100% water change than you are going to really have to be on your toes. First of all your filter and gravel can't dry up or you will lose those cultures and have to start from the beggining again. And like JSchmidt said, you can do a large scale water change, but you have to make sure that your water perameters are the same or very similar, and that you have enough bacteria in the tank to support the new water.

Vato - have you ever heard of auto-changers - commonly used in higher tech fish rooms, changing water effectively on a continuous basis to keep the highest possble water quality.

There is absolutely no downside to large water changes, provided that the pH/KH/GH/TDS of of the source water are comparable to the tank water. The only downside could occur in a poorly maintained tank where the conditions were approaching Old Tank Syndrome and changes would need to be started at smaller percentage changes to avoid osmotic shock.

100% partials are not ordinarily required other than situation of accidentally added toxins, but there is no such thing as the "bacterial colony" garbage that you are putting out. Many folk breeding fish are set for 100% or higher daily partials and I propmise you they have no water prpblems. Don't try to start new myths without having some idea of what you are talking about.

I'd recommend ditching the pH Down. Almost all fish that can handle ph of 7.2-7.3 will do fine in your tap water. Just be sure to add dechlorinator as you add the new water and you'll be fine. A water change of 10-30%is pretty modest and certainly won't harm your fish.

If you want to wean your fish off the artificially lowered pH, just do 5-10% changes daily or every other day with tap water. That way, you'll gradually lower pH without shocking your fish.

Good luck,
Jim

RTR I'm really not trying to start myths and I think I do know what I'm talking about. I have worked in two pet stores for over a year each, study extensively about freshwater aqauriums and I have a close friend who has been in the hobby for 50+ years who I talk with regularly. I honestly am not trying to start myths and, indeed it is important to maintain an amount of bacerial culture. For someone who is performing a 100% water change a day I can assume that they do not have chlorinated water, or have some sort of way proccesing the water. I live in the country and have my own well, therefore my water already contains an amount of bacterial culture, and the water perameters are close to those of my tank, so performing a large scale change is not much of a problem for me(I've only ever done an 80% change I'm not brave enough to do much more) but a person living in a city or a place with chemically treated water, there is a problem, ther will no longer have any bacterial culture. I can see how a large scale breeder can get away with large changes, because, ifrst of all, fish don't need the bacteria to survive, it is the water itself that bacteria is required. I know of chain pet stores that have sterilie water systems for this reason. But if you intend on keeping the water in the tank the water must have bacteria in it to prevent the spike of ammonia/nitrites/nitrates. I know what you are saying and I believe it is very valid. If I am still wrong I would apreciate it if you corrected me, so I can get my information striaght, and because I don't want to be the source of myths at all! I'm not trying to start a war here, so I'm sorry for possibly insulting you in any way, I hope there are no hard feelings.

I agree with RTR that very few of the bacteria are resident in the water column; most live in the gravel, in the filter, and on the other surfaces in the tank. If the water coming out of the tap is similar to the water already in your tank, therefore, your problems should be relatively non-existent even for major water changes.

That goes double for well water, not because it has bacteria in it (they test for that before they'll give your well a permit), but rather because it has no chlorine and is relatively chemically similar to the stuff already in your tank.

The only hesitation I would have is if your water contains chloramines instead of chlorine, because that chemical is more persistent and many of the popular water conditioners do not treat for it.