ID of Tropical Fish has no underscore

Hi, there's an issue with Tropical Fish where they have no underscore in their ID. and instead of saying "tropical_fish", it says, "tropicalfish". I always get this confused especially when I use command blocks. This is also inconsistent with other mobs which have underscores. Ex: "ender_dragon". (note: this report is talking about the Tropical Fish mob. The item(s) are okay.)

Steps to Reproduce

1. Make sure cheats are on
2. Type in /summon or any command related to Tropical Fish's ID
3. Search up "tropicalfish"
4. Observe how the ID has no underscore

Observed Results:
The Tropical Fish has no underscore, which is different than other mobs.

Expected Results:
The Tropical Fish does have an underscore, like other entities.

Here is a comparison between the mob and the item.