View Full Version : Cyano caused by old RO/DI filters?

10/29/2009, 03:32 PM
A year ago I moved and upgraded my tank to a 120 gallon and in the process I pretty much did a 90% water change. I have been battling cyano which I never had in my old tank. After researching a bit I came to the conclusion that my old RO/DI filters have bacteria growing in them and is feeding the cyano when I do my 20% water change every 2 weeks. My RO/DI filters are old, over a year. I never changed them because my TDS is still at zero. I just ordered replacements but I wanted to get others opinions on this matter.


10/29/2009, 03:43 PM
Personally I change all my prefilters every 6months but if you have 0 tds coming out of the unit that is not fueling your redslime.

10/29/2009, 03:52 PM
I thought the same thing, but couldnt bacteria still grow in the pre filters? the DI media doesnt filter that out right?

10/29/2009, 03:57 PM
the di filters out everything the prefilters and membrane don't therefore it will still be good water as long as the di is good, but it will use up the di a lot quicker