I saw a pc about 8 years ago submerged like that, but had live fresh water fish. It was right when water cooling was the rage for overclockers, but there were still issues with water leaks.
If you want fish in the tank it would be best to partition the tank, so that the PC ran in the back half and the fish were up in the front half in normal water.
I watched a thing on YouTube about this over a year ago. Its really expensive for the amount of mineral oil
And it doesn't bring the temp down at all unfortunately
it looks cool I will give it that