If i have 12 fish in a ten gallon aquarium how often would I have to change the water to keep them from dieng?

My bigger aquarium is messed up so I had to transfer then and I do not get my pay check for a couple of weeks, so how ofter would I have to change the water and such? Any thing else I should know? There are 4 corys, 3 swordtails, 3 tetras, and 2 molliesIf i have 12 fish in a ten gallon aquarium how often would I have to change the water to keep them from dieng?That is a big group for a ten gallon, but those are not big fish so you should be fine, as long as you get a new aquarium ASAP. First off, you should test your water to see if you need to change it, in order not to disturb the fish if you don't have to. You should also use the same filter media, gravel, and maybe plants. Don't wash them, especially in chlorinated tap water because you will kill the beneficial bacteria. You should change the water when the ammonia levels or nitrite levels raise to a level that stresses the fish or endangers them. You should also check the nitrate levels so they don't end up being too high. If you don't want to test the water (which I don't encourage) you should notice that the water is dirty, or smelly, or the fish are stressed, moving slow, etc. and then change the water. The only problem is if you notice the problem too late, it might also be too late to help the fish. So testing would be better. Anyway, since you already had a bigger aquarium you should know the basics. Buy a bigger aquarium though, or give some of the fish away if you cant... they should be in a good environment above all.If i have 12 fish in a ten gallon aquarium how often would I have to change the water to keep them from dieng?generally you need to empty about 30% of the water and refill it each week, just to keep the water cleaner.