not to stir up the pot... but a little edja ma catation for those who shy away from reseach..... at 13 cents pkh it costs about 60-90 CENTS PER MONTH TO RUN an AC70 (6w) penguins are electricity hogs at 1.50 per month... t-8 single strip lights ,,3 bucks a month ... the ONLY thing that really costs much is heating your tank that can run up the bill ... I LIVE IN PHX. so heating only a big deal for about 4 months a year....ANY WAY 6 tanks ...400 gallons... 20 bucks a month.. TOTAL... for 7-8 months a year.... 50-60 bucks total in the winter ... so unless you are using HI- END t-5 OR METAL LIGHTING your big electricity bill is coming from SOMEWHERE ELSE
It wouldn't waste much electricity but if the tank has already peaked in BB populations then its just a lot of clutter in the tank with no real benefit other than surface agitation. I do like the idea of having a couple in that tank that you can know throw in the other one to help kick start the cycle, though.
Dude likes his sponge filters ,and they look ok to him .plus they are great at tank start up time....and they cost virtually nothing to run.... I can't think of even one negative aspect to them ,this being the case..... oh and they ROCK as bio filters.