I have to agree with Nikki on this Charlie. One thing Cyano I can deal with it is easily harvested & one heck of an exporter, your tank would die without some levels of various alga's it is part of the required life, same with us. I have had kidney stones 5 to be exact they all hurt. Now here is the analogy part, they all are Calcium, so that would make you think to stop or closely guard your calcium intake right? Well not in every case, I can get all the natural calcium from foods, milk etc with entirely no problems BUTT if I take vitamins supplements of any kind, or even the added calcium in some foods BAM I get a nice Kidney Rock, and man yea it hurts. One other note, you had several things changed not just one, you removed a rock, stirred things up then split the rock then started doing large water changes to me I see three things that occurred maybe more that wasn't mentioned. I suspect you harvest your cyano until it goes away not doing anything else different than before all this. Once (month or two) things leveled off do One thing, change more water but do it one way or the other either do them as normally on your schedule but just double them & see what happened Or do the same amount as normal but double the frequency, then get back to us and then we have new science to study and learn. One other thing to consider is time, how long can you continue to do the same things that worked for years then suddenly things start changing for the wrong. What, why & how do I fix this? Over time your living system has become very comfortable but is this ok or do we need to reconsider our long term husbandry or maybe if you just continue as before exactly it will just go through another cycle.