I don't know much about plecs but are they egg layers, and how old are your babies
How much and how often do you feed?
and what?
We found that the more we fed the more they bred.
If we eased back on the food they slowed their rate of breeding - eg feed ever couple of days and they notice the reduced foor levels and stop making fry....
I can't imagine what vacum cleanings are like. The whole container the used water goes in to is probably like 3" thick of feces.