Question:

46 gallon tank -operating at 550 gph - if I had higher gph, would that result in me needing to change my water less often - I have a barebottom tank with four goldies in it - and I've come to the conclusion that in order to keep my fish healthy and active, I need to change my water TWICE a week 90% and 40% - if I don't, they begin to slow down, bottom sit, etc. So - a once a week water change is not enough even at 90% - would more filtration help keep my water cleaner?

whats your amonia, nitrate, nitrite and ph levels? You cannot judge the water quality without testing these.

a 90% water change every weeks seems extreamly over the top. usually a 30% every two weeks is sufficiant with a good filter.

Also have you considered that goldfish sleep. They do spend time sitting and resting, just like anyother animal.

You already have over 10 x gph which is good. What kind of filtration are you running? I have 20 x gph on my tanks yet still have to do 70%-80% waterchanges weekly to keep my nitrates at the 20ppm mark. For their continued (touch wood) good health, I will continue to do it this way

As long as your parameters are excellent, doing a nice big waterchange weekly should keep them healthy. Do you test your water before each waterchange? What are the parameters when you do this?

Also, do you have plenty of aeration in your tank?

The others questions are very valid. In a well cycled tank, you should be able to adjust the tank to a single nice change once a week or so.

That said, there is one more consideration..... Feeding. If you feed your fish less, they will produce less waste and the waste will produce less nitrates. This will make it possible to change out less water, less often.

If your tank is not cycled, then all bets are off - you will need to change constantly until your tank is properly cycled. I have had it take as long as 8 weeks for a cycle to work in some tanks.....

Rick at Goldfish Connection recommends doing only 25% water changes. He told me that doing more than 25% causes bumps in the cycle which makes it appear that more water changes are needed. I'm doing bigger water changes in one tank because of medication ruining the cycle, but I do 25% on the other two tanks. The nitrates have stabilized to a point that they never go above 20 over a 7 day period.

He also said that if nitrates go higher than 20 in 7 days the fish are overfed.

Just another point of view from another fishie expert - Rick - not me, lol.