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4 Feb 2010

I set up a 120l tank about 7 weeks ago and let it cycle for 5 weeks with 3 corys in it. I went through good and bad phases with water quality, sometimes crystal clear at other times milky. After 5 weeks the tank seems to have settled and the nitrite reading was at a steady 0. I had two filters on the tank. One biobox 2 with a 600l pump and an internal sponge filter. I added 3 discus and about 10 days later the water became really murky and the nitrite reading went up to 0.5 I did water changes and added bacteria however the fish did not look happy at all. I have since added a third filter, a fluval G3 and after 48hrs the water is crystal clear and the nitrite reading is 0 once again. Fish still do not look happy.

My question is, should I continue with water changes or will I just be removing beneficial bacteria? Also I have a separate triex cartridge for the G3 which I am currently not using. This is supposed to remove phosphate and nitrate. Should I replace this cartridge with the carbon one which is in the filter at the moment?

Replies would be really appreciated.

so doing a 50% water change at this stage would be beneficial? Also would the fish benefit from the triex cartridge?
Are you using ro water or tap? What is the ph and readings for the water. Because you have added fish the filter will have to adjust to the waste the discus put out. Discus can be really messy fish dependant on their diets.
I have a Rena 350 and I run 2xjbl filters in them. Their capacity is 1500lph and I had the filters running for over a month and half before introducing them.
I am using tap water however since I live near a RO plant (I live in Malta and most our tap water is produced from the sea) the water tends to have a ph of 7 give or take on the day. I now have the G3, the Biobox 2 and a sponge filter going full swing.
When I had juvenile discus and feeding beefheart I would do a partial 30% water change daily.
If I knew that the filters are ok and cycled well, then I would not have issues dong a 90% water change for this discus only tank. But the way the fish / filters are behaving at the moment I am at a bit of a loss....
Just keep at it. It will eventually balance.

Water changes are a good thing for growing discus.