trilinearmipmap,
You may be correct that the cyano was eating some of the ammonia (and a whole lot of phosphate). I cleaned the tank in anticipation of dropping the salinity to 1.010 to treat my fish for ich and did not want a die off of cyano to cause a large ammonia then nitrite spikes.
As it turned out, the fish did not carry ich with them, so I did not have to drop the salinity. There is now another healthy growth of cyano in the tank
, which cycled about two weeks ago before the cyano regained its foothold.
What I could do once the fish are back in the display tank in another ten days or so (gotta check the calendar), is drop the salinity for a week or two to see if the cyano in fact does die off. Knowing this would be useful if I had to treat new fish for ich in a Qtank that has cyano.
However, dropping salinity to find out the effect it has on cyano will not help me if new fish have velvet, a bacterial infection or whatever, which would require different treatments than hyposalinity. Before putting in new fish, I will probably still clean away the cyano anyway in anticipation of treating
any possible health problem and not having any spikes due to cyano die off.
What I won't do, though, while cleaning the cyano is have the two AquaClears running but will instead syphon the the tank dry, then immediately add NSW and get the system running right away. The foams won't get filthy from catching all the loose cyano and there will be no need to do a thorough foam cleaning. I will do a gentle foam cleaning to rid them of large pieces of crud, which is what I do each water change. Even though I suck out any poop I find in the bare tank 2-3 times a day, some of it still gets caught in the foams. Leaving the large crud in the foams is just asking for trouble, imo. You wouldn't believe how dirty a half bucket of water gets from even this partial cleaning
