25g is doable and you can save some money by skipping a skimmer which you can't really do on your larger tanks. Weekly water changes and proper maintenance are the key for running a small tank. And if youre not doing corals you can get by with cheapo lights too, the fish actually don't care.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.