Update:

Well, I managed to get two greenfin spotanus and started building up money. I have both food and environment at level two now and have paid for level three in food. I'm still at level one in advertising, but am not having any problems selling.

I have also bought the second tank, the aerator and the temperature regulator. I can't remember if/which plants and decorations right now, so will edit this post after checking.

I have played mostly either in half speed or two-times speed. Haven't had any die (actually, I've never had any die - even playing on my PC), but have had a few sick ones that I had to cure.

Just before starting this post I moved all adults into the sales tank, moved all babies into tank two and bought three batches of the pink (least expensive) eggs and got them going in tank one. Will be back to report on plants/decorations.

Edit: I only have the plant of nutrition. No other plants or decorations yet.