野生 and 生息: wild status and a possible habitat
Compare a wild deer and a bird returned to the wild with birds researched in a guide and a tank modeled on a habitable environment. Separate status, habitation, possibility, and reported actions.
A wild deer and a bird returned to the wild
野生（やせい） means wild or wildlife. 「川辺で野生の鹿を見かけた。」（We saw a wild deer by the river.） 野生の describes the deer's status, and 川辺で gives the location where it was seen.
「保護された鳥は元気になると野生へ戻された。」（Once healthy, the rescued bird was returned to the wild.） 保護された鳥 identifies the rescued bird, and 元気になると gives the sequence after it became healthy. 戻された is passive: it was returned to the wild, rather than actively returning on its own.
Research in a guide and a modeled environment
生息（せいそく） refers to habitation or inhabiting. 「図鑑で森に生息する鳥を調べた。」（I researched the birds that inhabit the forest in an illustrated guide.） The objects researched are birds that inhabit the forest. 図鑑で identifies the illustrated guide used, rather than direct observation in the field.
「水槽は小魚が生息できる環境を模している。」（The tank recreates an environment where small fish can live.） 生息できる expresses that small fish can live in the environment. 環境を模している describes what the tank recreates. The sentence does not establish fish already living in the tank.
Separating status, relationship, and possibility
野生 connects to the deer's status or the setting to which the bird was returned. 生息 connects to inhabiting a forest or an environment where fish can live. A forest or tank alone does not decide an animal's wild status or care history.
Researching birds in a guide, describing a modeled environment, and returning a healthy bird are different pieces of information. Preserve the possibility in できる rather than making it actual habitation already achieved.
Does 「水槽は小魚が生息できる環境を模している。」 establish that fish already live in the tank or are wild?
Show the answer and why
No. The tank recreates an environment where small fish can live. The sentence alone establishes neither their actual presence in the tank nor their wild status.