The jpg image is created from the raw image. You need to process the raw image to get a jpg.

Also use a high quality card for speed and reliability, everything else is mostly a marketing gimmick to get you to spend more.
Also it's digital not analog, so it's either there or its not, you won't retain any extra anything with a higher quality card.

Pictures are looking good, keep at it. Try using a remote strobe shooting down into the tank for fish pictures, it'll make the background look black or almost black.