It looks as though your biggest issue is the glass distortion caused by shooting at an angle through the tank glass.
As for RAW. the biggest difference is that a RAW file it between 12 and 16 bit. While a JPG is an 8bit file. Printers print in 8 bit. the idea of RAW is to allow the shooter to manipulate what 8bits are to be used rather than the camera software.
For the most point Canon, Nikon, Panasonic and so on invest millions on R&D to have the camera software be able to pick the correct 8bits. This is why for the average photographer RAW really isn't a big factor. Also you need to invest in some decent software such as lightroom to process a RAW file.
Some simple tricks to WB is to eliminate multiple colour temperatures. So if you run a 10K MH and some actinics, turn the actinics off for picture taking time.
and also try to white balance off of white.
J
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