aaronnorth said:
ceg4048 said:
Hi,
Personally I wouldn't worry about keeping any old water at all. As long as the water you put back in is clean and is at a decent temperature then it shouldn't matter at all. I do 90%-95% water changes all the time without any ill effect. Keeping old water is completely overrated and is an unnecessary bother which can result in a hernia. You should be able to do exactly the same as when you buy a fish from an LFS whose water is completely different from your own.
Cheers,
if the hardness is different then it could cause some major problems.
GH difference is never really a problem. Carbonate difference can theoretically be problematic, due to salt imbalance, but in practice I've never seen it have an adverse effect. Some shops keep their fish in RO water and I take the fish home, warm them up by floating the bag and release them into high KH/GH water without issues. The real problem is stress due to transportation issues as well as their adjustment to high CO2 water which is much more difficult.
Cheers,