One of the wonderful quirks of the English language is that we use the term aquarium to describe both a large scale tourist attraction as well as an individual water-filled vivarium (of any size).
In OSM, we have the tag tourism=aquarium which is supposed to be used only for the large-scale tourist attraction (i.e. multiple, large tanks, pay entry etc.). However, it does appear it is also being used for individual aquaria, which we might colloquially call a “fish tank”.
I’d like to see the large scale aquaria rendered in Carto (as they are important tourist attractions) but one of the issues is that there’s a mix of usage of this tag.
My suggestion is that:
tourism=aquarium is used only for the large scale tourist attraction (e.g., similar to a zoo or museum)
attraction=animal + animal=fish is used for individual fish tanks. These could be either located inside a tourism=aquarium or as stand-alone items such as a large fish tank in the centre of a shopping mall for instance
I’m unsure about tanks inside a pet shop (shop=pet + pet=fish) or restaurant. They could be tagged as attraction=animal + animal=fish but I’m not sure they’re really an “attraction” as we currently define it.
attraction=animal has an issue of being duplicated as area for the site, and points for animals inside. Am thinking attraction= could be used for the entire site of that topic, including the building or any structure, landscaping, walkways and waiting areas. Then exhibit= can be used for the fish tanks. (of course, if it is only a cage or tank in the open, they are the same) This may be compared with exhibit=artwork in =mall or =restaurant if used. Specifically, some eateries at zoo-type aquariums have an integrated fish tank inside or adjacent, for viewing while eating.
Another format to be aware of is some aquatic and “amphibious” animals are displayed with natural=water + water=pond on the ground. Semi-aquatic animal display areas can span multiple land and tank or pond areas.
Unknowingly, there are 8 https://taginfo.openstreetmap.org/tags/man_made=fish_tank and 1 https://taginfo.openstreetmap.org/tags/man_made=aquarium
I did some analysis of the current tagging of aquaria in OSM and posted in the Carto Github issue.
A short summary:
94.6% of the 1,232 instances did not contain “banned” words (associated with pet stores mostly).
At least 68.0% of instances with a name, were named as an aquarium (or similar) or I was able to manually verify that they were an aquarium through a web search.
52.4% were tagged as a building with an additional 7.7% tagged as a way or relation (likely larger exhibits with outdoor areas).
So it did seem to me that the majority of tourism=aquarium tags applied to larger tourist exhibits.
But it would be good to agree on how to tag individual tanks.