Same problem and I got this reply from an advisor.
Posted text:
Here is my standard post for algae or cyno control and elimination.
1. If you already use
RO water, test your source water. You may need to
add a deionizer to it. This is the most important step.
2. Siphon as much of it as you can. Breaking it up only helps it to
spread. You need to do this as frequently as possible.
3. Review your feeding habit. Are you overfeeding? Do the fish eat what
you put in at feeding time within a few minutes, or is there food lying
around the bottom after? Also, if you use frozen, make sure to drain
the as much of the packing juice as you can before adding.
4. Do you have adequate water movement? Any dead spaces in the tank?
Cyno has a harder time setting up in a system with brisk water movement.
5.Do you have a skimmer? If so, is it producing daily amount of dark
thick \"skimmage\'? Adding or upgrading a skimmer may help.
You can also run a
PO4 sponge which will help, but you need to address
the other underlying causes.
These are few of the key things that feed a cyno outbreak.
