The animals are what make ecospheres so great in my opinion. They can be really fascinating to watch and have the largest impact on the ecosystem. They are an integral part of the nutrient cycle and it is impossible to make an ecosphere without them. A lot of them feed off the plants and convert their nutrients into a form that can be reused. Other animals depend on other animals within the ecosphere. This is known as a food web. Unlike plants, there are only certain animals that I would recommend using in an ecosphere as some can be predatory or some may not be able to survive in a closed system due to additional needs. I will show both suitable organisms and unsuitable organisms so you know what to look out for. I would suggest using a large number of different species to maximise biodiversity.
Please note that it is important to have a sufficient amount of plants to sustain this biodiversity.
Copepods (Copepoda sp) and Common water fleas (Daphnia sp)
Mosquito (Culex pipiens) and midge larva (Culicoides impunctatus)
Water hoglouse (Asellus aquaticus)
Bladder snails (Physella acuta) and other pond snails
Dwarf flat ramshorn snails (Planorbis planorbis)
New Zealand mud snails (Potamopyrgus antipodarum)
Faucet snail (Bithynia tentaculata)
Malaysian trumpet snail (Melanoides tuberculata)
River limpet (Ancylus fluviatilis)