50% water change

That's what I do.....no problems here!

the only prob would be if the water conditions; pH & temp were altered significantly. other than that i imagine you have very happy fish

water changes to be done to suit your tank and fishes needs...if 50% a week works for you, then carry on. If you feel it is too much, then cut it down....there are advantages to cutting it down. As mentioned, temp, pH and hardness would be more stable, you wouldnt have to carry so much water around, the tank would get disturbed less....but i dont see any major problems with 50% a week, if you feel it is right.

if it would help, i'll let you know that i change 25% a month on my tank...some people would say that is far too little, but its what works for me and my fish. All the fish are healthy, water is crystal clear, water tests all com out good, excellent in fact. So its really what each individual tank needs.

Hope this helps.

And then breeders change 100-200% per day. There are few disadvantages to changing water, many advantages.

50% per week is fine...

RTR, at this point may i b bold enough to ask you to state these advantages?

It's a problem only if you amend the water with chemicals. A large water change in amended water can lead to large chemistry swing. If you do large water change routinely with no amendment, your water chemistry will approach that of your tap water.

Advantages include 1)the fact that your tank water approaches your tap water parameters excepting any pollutants developed since the last change - so in effect the more changes you do, the more and larger percentage changes you can do. 2) The water in the tank more closely approximates natural conditions (not native parameters, different thing) in that pollutants and waste do not linger in the area but are flushed out. 3) fresh water without pheromones and hormones and waste stimulates appetite and breeding. 4) in low KH water, nitrification destruction of buffering is not an issue. In higher KH water, downward pH drift is avoided. 5) in planted tanks, micronutrients are replenished. 6) Overall, the more frequently you partial and the larger volumes you do per partial, the more stable the tank water conditions will be.

Disadvantages are 1) that you have to do it. 2) If you are doing water modifications, you have to prepare more pre-modified water. 3) If you are doing infrequent changes, you cannot do large volumes due to possible differences in source and tank water.

HTH