If your going to keep any snake in the 75-gallon just make sure to clean it often and get a locking lid with some clamps...
Aside from that, rosy boas and rubber boas (their counterpart) make excellent pets. I have never owned one, but my friend had a few for awhile and I took care of them without any problems. Ate practically on command, and were docile as a dog.
Most North American ratsnakes also make good pets. They are a little more aggressive initially, but can easily be tamed. Fox snakes (I have one) are also great pets, incredibly docile and very good eaters.
If your out to get something really fun, jungle carpet pythons are very cool snakes that are somewhat large (5-7 ft) and very colorful. Sometimes they are a little snappy as young, but mine have been great pets and have not been aggressive at all.
There's alot of snakes out there, just pick some colors, do some research, and you'll be fine.
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Current Collection:
0.1 Antherystic elaphe guttata guttata - Corn Snake
1.0 Elaphe vulpina gloydi - Eastern Fox Snake
0.1 Elaphe obsoleta obsoleta - Black Rat Snake
0.1 Leucistic elaphe obsoleta linheimeri - Texas Ratsnake
1.1 Morelia spilota cheyni - Jungle Carpet Python
0.1 Tiliqua scincoides intermedia - Northern Blue Tongue Skink