Cyanobacteria is one of the most prolific forms of life in the world and the only true way to combat it is through out competing it. It can grow in almost any environment and under almost any light. There is no hobby light that can be considered anti-cyano.
Key factors in reduction are:
- increased flow
- decreased nutrients
- removal of any visible signs as soon as possible
I don't know how long your tank has been established but it sounds as if you are doing some dosing of different components for various reasons. It becomes increasingly difficult to make a recommendation without the interactions being considered.
IME staying on top of water changes, keeping flow high, reducing feedings and vacuuming out the cyano will stabilize the tank over a few weeks. All to often we are looking for FAST results.
I've also become a believer in Lanthanum Chloride as a method of reducing PO4. It's highly effective but must be utilized carefully to avoid any issue. dosing levels are relatively low.
Example:
I just set up a new DT at the house. I'm using new Marco Rock that was dry. It's known to leach PO4 for a while. New tanks are also known to be PO4 factories until all of the bacteria get into place and at levels that are needed maintain balance. I am NOT big on dosing stuff or on additives and believe that time is the best cure for a new tank......
2 days ago my PO4 was 0.31ppm
I setup an LaCl drip into my filtersock compartment. I used a 3ml per liter mix and dripped it over the course of about 24 hours. The next day the PO4 registered 17 on my Hanna ULR which is a level 0.05ppm. Still a bit high but not out of the ball park. I am positive that the PO4 will be back up in a few days but I will likely knock it down again. Eventually the tank will mature and this will not be an issue.
Well said and summarized.
The most challenging of all that is the patience honestly!!!!