Robert Goldstein says in his Marine Reef Aquarium Handbook that only phosphate starvation would be a suitable way to eliminate it.
But I still haven't got a proper phosphate kit like the one from Merck. With all the usual ones it's really a guessing game as they don't go to concentrations that low or the colours on the charts at those concentrations are almost similar.
Those bacteria are always present but form large chains and chunks for reasons often difficult to understand.
There is often mentioned a mysterious nitrate to phosphate ratio of 16:1 but I don't understand that if the cyanos are able to get nitrogen from dissolved nitrogen gas.
If it's in a nano tank and it doesn't cover much sensible parts in the tank as with me I simply harvest that slimy sheets like any other nuissance algae. That way, I export nitrates and phospates out oft my tank, too.
The only animals that presumably have suffered from those cyanos are a few syconoid sponges but they are quite prolific in my nano and spread like mad.
Also, I saw that the cyanos keep magically a distance from the rocks.
When I harvest them, mostly when I do water changes, I get them out with tweezers or a turkey baster and I empty the turkey baster into in a small vessel to have a measure how much salt water I have taken out to substract that from the amount for the water change.
Once, it let that vessel stay for hours and I saw then that all the cyano particles had gathered to only two big lumps.
So, they attract each other to form those large colonies.
In the pico I have set up recently, I saw that a Chaetomorpha ball in very strong water flow is completely free of cyanos but they come back onto this algae when the ball is in low flow.
I don't know if this is simply because they cannot attach in high flow or they get their enzymes washed out from their coating and they are starving then.
Only in my nano it is incredibly difficult to adjust the already three vertically streaming powerheads to establish a good flow on the sandbed in every part of the tank without producing sandstorms.
So, I guess that there are only three ways: getting to 0.04 ppm phosphates or having everywhere in the tank a strong water flow or always harvesting those cyanos.
. This thing has been up and running successfully for about a year now, has survived a move, and apart from a small issue with cyano a couple of months back, no crashes or problems. The only inhabitant, besides a couple of hermits and snails, is an Odontodactylus havanensis mantis shrimp.
