I don't have the dimensions since I don't use one but it will NOT overpower a 29G tank. I use a under tank sump/fuge for all my systems but these work well for what they are intended. MP did a great job on this DIY thread.
You will need at least 4" of clearence behind your tank.
__________________
I wonder how much salt mix I would need to turn our in ground pool into a Reef. 
|