These how to guides are published courtesy of OATA (Ornamental aquatic trade association.) OATA - Ornamental Aquatic Trade Association LogoThey are all Adobe PDF files and can be downloaded, and printed if required, just click the title you require, (this will open a new window).
They provide accurate and easy to follow information on how to care for many species. These are added and updated often.

Set up and water testing

1 How to set up and maintain a freshwater aquarium
2 How to set up and maintain a marine aquarium
3 Understand & test water quality

Pond and pond fish care

Set up and maintain a wildlife pond
Setting up your pond
Make your pond safe
12 How to care for pond fish

Coldwater fish care

10 How to care for Goldfish in aquariums
11 How to care for Fancy Goldfish

Tropical fish care

20 Hillstream Loach, White Clouds & Weather Loach
21 Tetras, Rasboras & Danios
22 Guppies, Mollies & Platies
23 Barbs
24 Bettas, Gourami’s & Paradise Fish
25 Rainbow Fish
26 Freshwater Sharks
27 Dwarf Cichlids
28 Discus
29 American Cichlids 
30 Malawi Cichlids
31 Freshwater Stingrays, Knife Fish & Elephant Nose
32 Piranha, Snakeheads & other aggressive species
33 Catfish
34 Tropical algae eaters
35 Killifish
36 Loaches
37 Wild caught freshwater fish
38 Tankbusters

Freshwater invertebrates & plants

50 Shrimps & snails
51 Crayfish & Crabs
52 Aquarium Plants

Brackish Water Fish

60 Brackish Water Fish

Marine fish and invertebrate care

70 Clownfish, Damselfish, Chromis & Basslets
71 Blennies, Gobies, Jawfish, Dwarf Wrasse & Firefish
72 Butterfly’s & Tangs
73 Dwarf Angelfish
74 Large Marine Angelfish
75 Seahorses & Pipefish
76 Groupers, Morays, Triggerfish & other large marine fish
77 Venomous & poisonous marine species
90 Corals
91 Anemones
92 Marine molluscs, crabs & shrimps
93 Starfish, sea urchins & cucumbers

Aquatic reptile care

100 Terrapins & turtles