Great looking gerbils. They will chew out of that cage in no time. One think I would suggest is movign them into a tank with about 5-6 inches of bedding. Gerbils love to dig and burrow and would prefer alot of bedding with untreated wood hides. Plastic would just get chewed up and there is the chance they could ingest a chunk of plastic and get a blockage.
One thing we did with my brother's gerbil is we put toilet paper and paper towell rolls in there cages. We would watch the little demon shred that in 10 minutes.