It's weird that 15 gallon tanks aren't included. I was able to buy one roughly a year ago when the employee just keyed in the price. A later attempt failed. Of course it was a karma disaster as the tank had a small chip in the corner that later turned into a full diagonal crack in the middle of the night, leaking about 10 gallons onto my floor by morning. Fish were saved, but I wasn't too happy about the cleanup. Replaced it with a 20H on their next $1 sale.