I think your biggest issue is going to be writing an actual book. I took up trying to write a better book on sharks/rays in captivity a year or two ago, and actually got decently far with it. It's hard - really hard. Species profiles took much longer than I thought - formatting them, deciding what info to actually include, making sure that things didn't constantly repeat. Pictures were tough to get - you need credit and permission if they're going to be published. Then you've got to figure out how to format things through the rest of the book. There are some things you can talk about for pages and pages and need to thin out. Then there are other things that you can't even fill a page with, and need to find another section to include them in.
This takes a lot of time. I rewrote that book at least two or three times before realizing I just didn't have the time or energy to write it.
islandguy11
covered the Youtube guys pretty well, I really don't have much else to say there - he spoke my mind.
Here's my suggestion to you. Write a draft of a care profile for ONE fish. Redtail cats, tiger shovelnose, arapaima, arowana, whatever you want. Choose a single fish and write a full profile on it, post it here and see how it goes. See how you like it, post it and let others see how it turned out.
I don't have any of my book pages left, but I remember pretty much how I had them set up. Feel free to PM me and I can help you with a format.