Turn pumps off 5 minutes before shooting.
Use a tripod. That's pretty much mandatory if you want a decent close up macro shot that isnt slightly blurred by you moving the camera.
With tripod use, drop ISO as low as possible. A reasonably high f stop, like f/11 or so, is nice for getting some decent depth of field. This will most likely mean shutter speed of 1/2 second or so, but that's fine since you're on a tripod.
Shoot perfectly perpendicular to the glass. Otherwise you fight distortion which you cannot correct in Photoshop.
Manual white balance. Shoot in RAW if possible, adjust in software later.
Those few things should give you a lot to play with.
Once you've got those down, then work on getting a better subject. All your shots, with possibly the exception of the clam, have so many other objects (corals, rock, fish, etc...) around that it's just a super busy picture and nothing really draws our eye to look at any certain aspect of the picture.
If you can isolate your subject by either being real close macro so nothing else shows, or else move the subject away from other things and shoot it there, then you'll have a more pleasing to the human eye photograph.