I have sold some of the fourth magic fish without any problems. I now have two of magic fish numbers one, two and three, and four of number four. All pregnant and split 5/5 between tanks one and two.
I also paid for level two of advertising, but put it on 1/2 time. All fish are fed and healthy, so should be fine for 10 - 12 hours. Hopefully, at that time I'll have level two in advertising and several more fish to sell.
If all goes well, do you think I should then buy level three in advertising (just sticking with raising and selling magic fish 1-4) to see what happens after that?