Mature Tank

[dwarfgourami]

Where did you get the information about doing a 90% water change?

I see nothing seriously wrong with that- after a fishless cycle you do a major water change (70-90% usually recommended) to dilute the nitrates that are left by the nitrite-eating bacteria.

90% is A LOT. How the hell are you going to keep the filter running?

Most of us switch the tank electrics off before we do a water change. It doesn't take long to take out 70 ltrs or so (depending on the size of the tank) with an efficient syphon; the filter bacteria will survive that long without serious damage. And as most of the bacteria live in the filter media, not in the water column, you needn't worry about losing them through the water change.

 

[Tolak]

Check out biological exclusion in this post; http/www.fishforums.net/index.php?showto...gical+exclusion