I added a sump/fuge to my 29g biocube this week. Bought a used 14g biocube and it fits perfectly in the 29g stand. I left the built in factory chambers on the 14g and use them for the separate areas of the sump. The water drains into 14g chamber 1, then flows into 14g display area where i will keep algae, overflows into chamber 3, and i put my return pump in chamber 2. It has been running for 3 days with no problems.