One can certainly feed a diet taken from the sea... but seriously?
If your goal is to become less carbon-emitting... kinda defeats the purpose.

Krill is as low on the food chain as the ocean gets. It feeds a good many things we like to eat. I say leave it where it is... and adapt your produce for feed.

In addition, cold water fish are a little rough to handle in Texas... unless you are someplace where you can mitigate the heat exchange.

There are a number of ways to do it-- bury the tanks, (messy, but workable) insulate the tanks (earth is cheap... but so are a number of other things, like newspaper bundles, bales of hay... not attractive, but can be 'concealed' behind a lovely frame of something folks won't fry over) or be willing to 'refrigerate' to a degree.

Warm water fish- tilapia, catfish... or carp, if you aren't interested in eating (although I hear a couple of carp species are being used as white fish) will tolerate the heat, grow at a reasonable rate, and be table ready in 4-6 mo. [Catfish, I hear, take a little longer... but the longer you let 'em grow... the bigger the filet!]