Oh ok, my understanding was LC is a way you can bolster carbon levels to make sure there isn't a short fall, unless you've got flora or fauna that are extra sensitive to it (sensitive shrimp, Vallis etc). It's not really just treating the symptom if the root cause is a short fall of carbon, although I take your point about balancing light levels to fauna's tolerance of co2 first. I've been dosing LC at 3/4 recommended level since the start of the tank with no ill effects (bar some damage to Riccardia right at the beginning when I painted it on directly to treat fungus on the wood). It seems unlikely it is the cause of the Otto's behaviour currently, since the level has been stable since almost the start.