I was surprised when I found my RETFs at Petco too. The Petco here in KY had 5 and I bought 2 and put them in a 12x12x18 ExoTerra. Like you, I plan on upgrading the tank in the near future. I'm planning the upgrade around Christmas time. I might go with the 18x18x24. I hope they will be okay in the smaller tank for now. Good luck!