Baensch Atlas of Freshwater Fishes volume 1 has most of what you need in it. There is information on filter cycles, basic plants, diseases and a lot of common fish. The other volumes are either saltwater fishes or uncommon freshwater fishes, and new species of fish and plants.
The Manual of Fish Health is good for diseases.
If you want a good book for identifying species, the TFH Atlas of freshwater fishes is worth grabbing, although they used to cost a lot (about $400 back last century). They also do a saltwater atlas.
When you start to specialise in a particular group of fish, then you start buying books that are specifically about those fish. When I started keeping Australian native fishes, I got any book I could find about natives and then books on rainbowfish, then joined ANGFA and got newsletters and Fishes of SAHUL from them.
I had a few books on Rift Lake cichlids, Labyrinths, Discus and various other groups of fish. Basically whatever interested me at the time is what I bought in the way of fish and books.
I bought a few coral books including a coral identification guide that came in 3 books and they were big and heavy
A guy in ANGFA worked at The Aquarium of WA and did a talk at ANGFA about jellyfish or something and he had a lovely book on Invertebrate Zoology. I managed to get a copy of that from Curtain University and it was big, heavy and hideously expensive (over $500). They had some other nice books there too but I could only carry that one book home because it weighed heaps.
I also collected fish magazines, you can get them in digital format now and it's cheaper than paperback.
I did the same thing when I was keeping birds back in the 1970s and 80s. I got a few books on commonly kept birds (most were American or European). Then a magazine called Australian Birdkeeper Magazine came out and I got all of those for 20 years. A number of Australians that kept birds started writing bird books too around that time and there were books specialising in Australian finches, Neophema parrots, Cockatoos, etc. I had a field day back then and bought anything that looked good.
There used to be a secondhand bookshop in America called Seahorse or something like that. they used to have a lot of secondhand fish books and magazines and they were cheap too. I can't find them online but hopefully they are still around.
Currently I view the CSIRO bookshop online
CSIRO PUBLISHING has an international reputation for quality educational and reference books and CD-ROMs in the subject areas of agriculture, biology, botany, forestry, ornithology, zoology, marine science, freshwater science, plant science, soil science, natural history, ecology, environment...
www.publish.csiro.au