I don't use them/ unable to recommend
Cuc don't do much other than add waste to the system. Source for statement: the nuisance algae forum where eighty currently wrecked tanks already have a cuc and are still wrecked and usually even the beyond methods aren't working, see the multiple page attempts underway
If cuc's worked other than from one person testimony (got lucky) that entire forum would have no tanks to fix.
They do work. You just need the right diversity of them. They barely add waste. That "source" is also not a source. They literally are what eat algae. Have enough that prefer the right algae in a tank, and you don't get algal blooms assuming waste is in check. Its literally nature 101 on how algae is limited in growth (predation and needed molecules)