Its all about the surface area... A 4' deep 5500 gallon pool is much different than a 2' deep 5500 gallon pool. What he is saying is true though, cownose do express stress symptoms with less room to move. I generally keep my babies in a very shallow 1000 gallon till they are eating well and putting on weight then move them to a pool that is around 3000 gallons til they are around 12" in length. Then they go into a pool wit adult females around 10,000 gallons (birthing pool) until they are ready for the big show. I feel adults can be fine for life in a properly planned out 7000 gallon pool.