I've had problems maintaining cheato in my system as well. Many things can cause it to melt away, but one big one is the lack of nutrients for it to survive. Test your nitrates and phosphates to see what the levels are in the tank.
Thank you. I've checked my nitrates they are ok. I have a phosphate reactor. I do need to buy a phosphate checker. I'll look futer into what you've said
I am having the same problem too. I have watched this happen at least one time (could be more) a year when everyone appears to have an inordinate loss of chaeto.. I have a chaeto reactor and because I am having a hard I’m finding it now, I use floss along with small amounts of chaeto.