You got a great deal. The tank cleaned up real nice too. Lot of good planning also. So to stop back siphon from the return. You drill a small hole just at or below the water line. when the water drops to the hole it sucks air & breaks the siphon. Check out the term "siphon breaks" . I love my 75. just the right size for a decent display & ease of maintenance. Sounds like it will be a while before You convince Your Lady into a bigger tank !