I's a company I'm trying to start in my spare time.
I have a test project a ran at a retirement home, I place, maintain, and do all work on a nice aquascaped aquarium. It stays my property bet startup is free this way. I gave them a 3 month free trail and after they signed for the next 4 years. Small monthly fee, zero work of maintenance for them, all troubles are mine to solve.
Regarding difference from the US:
Fish are cheap, all the rest is expensive. Some things are crazy expense, like neocaridina can be 5-10 euro a peace in a shop (average net wage here is 2.500). rocks are almost €10 a a kilo from a shop, wood €30-40 a kilo. so a 40G aquascape with lots of hardscape, external filter and CO2 is a full months wage.
Fuel/gas/electricity is very expensive compared to US, houses are very well build and insulated so I focus on +-22° room temperature setups.
Selling animals as a hobbyist is illegal on almost all online platforms, and those were it is legal you can't have a permanent offer for example 3 kinds of shrimp. Occasional and unforeseen sale online is allowed, when there is frequent or structural sale (very vague in the law) it's illegal and you need to have a company.
wild caught is rare, most fish here are bred in eastern Europe where wages and power costs are low, so large breeders are rare in western Europe. Most shops only carry 20-40 spices, some hidden gems (many distributors for shops open for retail also) carry few hundred spices and almost all basic spices can be ordered vie local shops on a week notice. for example killifish, some shops have one species in stock, one distributor has like 5 species, but it's hard to get anything that is rare.
The r/shittyaquariums here seem to be as frequent as in the US, awareness about fish care and planted tank is limited to hobbyists only but many households have there abusive fish tank.