I am aware of a lot of shops that specialise in "reptiles", and sell frogs etc. Far more of these than specialist aquatic plant shops; possibly even more than dedicated marine shops.I think their simplicity can become addictive. Simple terraria is easy to achieve in just about any container.
I’m looking more toward vivaria for the purpose of housing Dart frogs or small lizards like the Day gecko.
I know keeping Dart frogs is a bigger in the states. But I’d be intrigued to know how big it is here in the UK.
As their requirement's overlap a lot, I think as a group they prop eachother up. (reptiles, amphibs, insects etc)
I was thinking about buying a pet shop, once (you know, ditch the real world, and keep budgies etc) I vaguely remember that on their books 2.5% of customers were buying for their repltiles/amphibians; ~20% fish, ~38% dog, ~35% cat, i'm a bit out, but the bottom 5% was reptiles/amphibians/tortoises/turtle and insects. That 5% was still a good earner, and in the local area it competed with two dedicated shops (which are still going!).