Cyano Will Not Go Away

[Mr._Fishy]

I managed to get some cyano in my 29g tank about a year ago when it was planted, I believe from low nitrates. It is now no longer planted with the exception of some anubias. My problem is I cannot get this to go away. I've done repeated blackouts and dosed with maracyn but it will not go away. After the blackout it seems as if it's gone or almost all gone but within a couple weeks it's back. My tank is being turned over around 8x per hour so I can't imagine it's because of low flow. My water quality is good (for a messy eating pred tank).

Any other suggestions as to what to do?

 

[aaronnorth]

buy some dry powders - potassium nitrate (KNO3) and dose that to raise the nitrate abit. Aim for about 10ppm, or just leave the waterchanges for longer so it builds up.

keep the filters and substrate clean - if there is any debris it will rot and produce ammonia.

try taping the bottom of the tank so it blocks light to the substrate (you only need to do it so it covers the substrate), unless the tank already has something there.

EDIT: just saw the "messy eating pred tank"

It might not be low nitrates, but ratehr an amomia spike, if they are excreting lots of waste or feeding lots.

 

[Mr._Fishy]

I'm thinking it wasn't an ammonia spike as I first got it when I ran out of potassium nitrate for about 3 weeks. When the tank was planted the nitrates were usually somewhere in the 5-15 ppm range at a water change while using ferts. I don't remember what it was for the few weeks that I ran out of potassium nitrate, although I'd imagine it was pretty low. Now that the tank isn't planted the nitrates are usually somewhere around 20-25 at a water change.