Why not just add another HOB
? Easier, safer and if you need a backup on a QT/additional tank, it's ready to go.
's used to be the only filtration you could get, now they're rarely used IMO
. The problem I see with them is they don't really take anything out of the tank, they just hold it via vacuum under the gravel (can't use sand with UGF
from what I've read), but if your pump fails then all that gunk could become suspended and create all kinds of troubles IMO