How often should I change the water in my 10-gallon aquarium tank?

No. You should take your fish out! Take your two Goldfish out, your 10 gallon tank is only big enough for one of them! Even though it seems like they can all live together in the tank, it is in fact way too small. Ryukins need 10-15 gallons of water each, just to be happy and live a long time! I suggest you go out and buy a 40 gallon tank for your three fish, or you return two of them. You should be doing 25% water changes every week. You should NEVER do a 100% water change, you need that bacteria in your tank!  more

Goldfish really should. be kept in at least twenty gallons per fish. I know that, esp since they're small, it looks like they'll fit, and that they cram all those poor things together in pet stores, but they are MESSY fish, and no matter how much you change the water there will be ammonia build up. its from them pooping and even breathing through their gills. It is possible to keep it in a ten, but please don't add any more fish. Plus, Ryukin goldfish can be eight inches. But seriously, they are one of the messiest fish in the hobby. Three will make them stunted, and the water will be nasty. If you keep the one in there, change the water 50 percent once a week, and having a high powered carbonated filter will help. Then every four weeks, instead of doing a 100 %, mix about twenty percent of the old water with the clean water. hundred percent water changes are never good.  more

omg you are so mean to the gold fish first 1 non cycled tank 2 to many goldfish 3 to big of a fish 4 never change 100% of the water 5 adding gold fish to fast 6 to small of a tank should i keep on going  more

small frequent changes, once a week and good maintenance, algae, light control, do not overfeed; do not do total changes b/c you rid your tank of beneficial bacteria; I would not add any more fish or it over taxes a tank system; live plants can remove nitrates caused from excess food, waste etc ; consistent weekly maintenance in smaller amounts, remove chlorine from water ; change filter media or you just reintroduce the bad stuff into the tank when the filter media gets over saturated with waste ; good luck  more