Tiny creatures, reminiscent of worms but featuring miniature hands, have appeared in my 16-gallon saltwater aquarium.

[christianomoshar]

Hello! Recently, I've noticed tiny creatures in my 16-gallon saltwater aquarium, similar to worms but with miniature hands. They've been consistently present in my filter during changes. Unlike the ones in videos, mine walk between rocks and don't swim. Any insights on what they are and if they're safe? Water levels are generally good, except for slightly elevated potassium.

Also, I've encountered brown-red algae in my tank. Despite regular water changes, it appeared around the time my crab mysteriously vanished. Any advice on eliminating this algae? I've had the tank for 3 years, previously dealing with dark green-black algae. My fire shrimp, a heavy fish food consumer, lived for 2 years but recently passed away. Any potential issues from not having the shrimp around anymore?

 

[KrisReef]

Those are some kind of marine pod, (amphipods?) and they are the worst thing that you could have if you don't like good bugs in your marine aquarium. They are great natural food for fishes and signal a healthy reef system is developing. The algae will hopefully disappear, it might be diatoms actually but manual removal with water changes and time generally these things will pass away on their own. Patience and hand cleaning are my own least favorite parts of this hobby.