Right now with all of those fish I would be doing a water change (maybe 20% or 4-5 litres) every day for the next while. This will help the fish survive the cycling or nitrogen cycle that is being established in your tank.
The problem with goldfish is that they are cool water fish. Cooler water has more oxygen disolved in it for the fish to breathe. They can be fine in warmer water but it will require you to do far more water changes. Perhaps every other day to keep them healthy.
The only chemical you need to add is a dechlorinator assuming you are using water that has chlorine in it (such as city water in North America). If it doesn't have that added to it then you can just try to match the temperature as close as possible and change the water.
Angel fish can get to be up to 8 inches or maybe 20 cm high or so if properly kept. So a taller bigger tank is a good idea when you get the chance.
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You could keep a small school of tetras (mayeb 5 at most) int he 25L tank if you wanted to have 2 tanks going at the same time.
The problem with goldfish is that they are cool water fish. Cooler water has more oxygen disolved in it for the fish to breathe. They can be fine in warmer water but it will require you to do far more water changes. Perhaps every other day to keep them healthy.
The only chemical you need to add is a dechlorinator assuming you are using water that has chlorine in it (such as city water in North America). If it doesn't have that added to it then you can just try to match the temperature as close as possible and change the water.
Angel fish can get to be up to 8 inches or maybe 20 cm high or so if properly kept. So a taller bigger tank is a good idea when you get the chance.
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You could keep a small school of tetras (mayeb 5 at most) int he 25L tank if you wanted to have 2 tanks going at the same time.
