I'm another one who's 'into fish' as my OH puts it and was a moderator on a fish forum so i'll just post a few snippets of info, hints and tips to try and help you with your next lot of fishy friends:
Setting up the tank:
*Always use de-chlorinator on tap water before adding to the tank, if you run out, leave the tap water in a bucket for 24hrs as chlorine levels will fall when the water is exposed to air.
*Always use a filter and ensure that it is suitable for the tank volume, a slightly bigger filter can allow you to keep more fish in the tank but don't push it.
*Allow the tank to cycle, either with or without fish (Google 'How to cycle a fish tank' and 'The Nitrogen Cycle in Aquariums' for full details on this process), and invest in a small water testing kit that includes tests for Ammonia, Nitrites, Nitrates and pH.
NB: The quickest way to 'cycle' a tank is to borrow another filter sponge from an established tank and squeeze it into the tank water to transfer the bacteria.
*Decide on a Coldwater (no heater) or Tropical (with heater) environment and buy appropriate heater if required.
*Decide on what fish to keep before going to the fish store! It's like going food shopping with the munchies otherwise
, all the pretty colours, etc. can lead to money wasted and dead fish
*Decorations/sand/gravel are all totally personal choice and the fish won't really care that much as long as there are holes to hide if there's a mix of fish.
Stocking the Tank:
Tropical (21c - 26c): (ie, Neon Tetras, etc.)
*Try and follow the general guideline of 1" of fish per gallon of tank water, ie. a 20 gallon tank can support 20" of fish.
*When getting the fish a bit of research will do wonders as, like anything else, some fish just don't like each other, some are aggressive, some need hidey holes, some have to be in a shoal, etc.
Coldwater (16c - 20c): (ie, Goldfish)
*Try and follow the general guideline of 20 gallons of tank water for the first fish and 10 gallons for each fish thereafter. Sounds a lot? Coldwater fish are
messy and need the extra water/filtration to cope with it. These types of fish are not strictly aquarium fish but pond fish and when kept in aquariums they suffer from stunted growth and shortened lives so if you keep them you need to try and give them the best chance.
*Bear in mind that an aquarium in a house is very hard to keep within the 'coldwater' threshold during summer, for this reason Tropical fish are regarded as easier to keep.
Buying Fish:
*Check the shops tanks for dead fish, if you see any don't buy.
*Check that the pet shop is against dying fish (the practise of injecting dye into fish to make them a bright, pretty colour which only guarantees death within months), there should be a sign in the window if they are against the practice.
*Ask about their quarrantine proceedure, this is vital if you are adding fish to an existing aquarium already stocked.
*Ask questions you know the answers to, if they don't know their stuff you can't trust their advice so you're on your own with decisions.
*A good fish seller should ask you about your tank so be prepared with all your stats
Regardless of what type of fish you are going to keep the introduction method is the same:
*Float the fishbag in the tank to equalise the water temps inside and out
*Open the bag and allow some tankwater into the bag while still floating
*Gradually exchange the water in the bag before finally letting the fishies swim into their new home by dipping the bag under the surface.
Feeding:
*Adding too much food is more dangerous than adding to little! Excess food decomposes and causes Ammonia levels to rise to lethal doses so again a bit of web research on your fish will help here.
*Fish will be fine for up to one week without food as long as they are gradually starved down and then fed back up. The week before you go away gradually decrease the amount of food the fish get and then when you get back gradually pick the feeding back up over a week. Don't use the food blocks as the contain mostly calcium carbonate which disrupts the water pH and also causes Ammonia spikes as you have in effect just dumped a load of food in the tank
Cleaning:
*Aim to change approx. 20% of the tank water every two weeks (minimum) with fresh water, highly stocked tanks may benefit more from a 10% change every week.
*Clean the filter sponge every two weeks by squeezing it in the old tank water that has been removed before you throw it away.
*Clean any fish poo off the gravel/sand
*Wipe the glass with a magnetic scrubber (easiest way)
I hope some of this was of help and wasn't too
but I do like fishies