from my understanding "vibrant" aquarium cleaner is a carbon source. possibly what is feeding the cyanobacteria?? that's where id start! this is common for new problems to start while dealing with old ones especialy true in the case of dosing carbon sources. word to the wise, if you are unsure of what your dosing -don't do it. water changes and general husbandry is way cheaper ,in the long run. I use no po x right now and for me its working. I started with a super low dose of 10ml for the whole system( approx. 350g after accounting for rock/sand) the directions said 3ml per 25g. that's 42ml to start if id have done that I too would have the lovely red cyano. start carbon VERY slowly and it could work for you. hope that was helpful.