I have had my 3 gallon tank for about 4 weeks now and the store told me to change the water about once a month. But since this is my first tank I'm not exactly sure how much to take out or how much to put in. And when I do put the water in should I just use the same type of water that I originally filled my tank with?

__________________
90 gallon mixed reef
20 gallon cichlid tank(soon to be an SPS tank!)
14 gallon (saltwater) Biocube &
10 gallon nano reef tank!

thanks for the quick reply!
I just remembered another question that I would like to ask, is distilled water(for example the gallon jugs you get at publix) ok to add to the tank when I change the water?

__________________
90 gallon mixed reef
20 gallon cichlid tank(soon to be an SPS tank!)
14 gallon (saltwater) Biocube &
10 gallon nano reef tank!

No you should not use distilled water but if you want to buy water to be safe you can use SPRING water. Distilled water has some things removed from it that the fish actually need to keep healthy so you should not use it.

The spring water is usually okay to use without any conditioner and is safe to use in all tanks.

I have used it during the summer when the nitrate levels in my community are high due to fertilizers being used in the area and making our nitrate levels high in the ground water so our tap water is not safe.

Rose

Welcome to the forum Kris.
Distilled water has no minerals at all in it. If you have exceptionally hard water, you can soften it a bit by mixing distilled water with your tap water, but straight distilled water will kill your fish. Fish need a reasonable mineral content in their water to survive. Even "spring water" is often too pure for fish to live in. It depends on how the water is filtered and treated before it comes to you. I would at least test so called spring water before using it in a tank. When I worked doing some water testing in an industrial lab, I took a few samples of the bottled drinking water that was in the water cooler. It was almost as pure as distilled water. I am sure each supplier has their own way of making drinking water but that stuff would have been way too low in TDS for most fish to survive. If your tap water is not too bad, use it and the fish will be fine.
In a 3 gallon tank I would be changing a gallon a week, especially if you have a significant fish load in it. Anything more than a single betta is starting to get to be a heavy biological load for a tank that size.

__________________
Fishless cycling

Thank you!

__________________
90 gallon mixed reef
20 gallon cichlid tank(soon to be an SPS tank!)
14 gallon (saltwater) Biocube &
10 gallon nano reef tank!