You're absolutely correct, and I did think about the cyano. But my reasoning is this. Cyano can be caused by an excess of carbon. It can also be caused by an excess of nutrients. Since he is not carbon dosing, the current cause of cyano is definitely not the former. It therefore has to be the latter. Carbon, skim and siphon. I don't believe the test kits. Once thing start improving, if cyano starts coming back, then we can worry about carbon causing cyano. If you're really worried about it, use vinegar, GAA, or a bottle of Zeostart. They're much less likely to encourage cyano.