I think the pics look good!
I am by no means a professional, but in my experience there are a few things you could try to help increase the sharpness. Try turning off all your pumps before you shoot. This will allow you to use shower shutter speeds (but try to keep it above 1/100) and higher apertures (typically all glass is sharpest when stopped down). Try keeping your lens perpendicular to the glass. Otherwise it will cause refraction around the edges (like the last zoanthid photo) Refraction also is highest with multiple light sources such as dawn dusk settings where the bulbs give an uneven light because of the bulb position. Lastly, if you have a "live view" feature, zoom all the way in and tune your focus manually before releasing the shutter. Hope this helps!