I have some new fish coming this week, and I'm looking for some of your opinions on my options for housing them. My intention was to use a 40 breeder, but I also have a 55 available to me as well. I like the 18" depth of the 40 breeder, but my gut says to use the 55 for the extra length. FWIW, the fish are 3m/9f Metriaclima Elongatus Chailosi, and will be the only inhabitants. Thoughts?