What in the world is this?

[Nehemiah]

It's a nano tank that's still cycling with live rock from TBS (I think, I bought the tank, rock, and macro algae as a kit?). It's been rough going since I knew absolutely nothing about marine aquariums when I got it but parameters seem to be stabilizing, albeit slowly, and now I have a bit of hair algae, diatoms, and all sorts of strange things are popping up.
Most I have identified, but nothing online looks like these at all and now there are a ton of them.
They start off extremely tiny, opaque white, staying on the glass mostly. I don't have a camera that can accurately capture this stage.
Now that they're large they seem to be grazing on the macro algae instead of the glass. They remind me of scale insects on houseplants. I'm not sure if they're actually eating the macro or just the algae and detritus growing on it. they look like they have a lot of short tiny legs on each side of their body.
I'm pretty sure I saw one literally jump from one macro to another too.
Any ideas? it's really bothering me not knowing

TIA!

 

[Euphyllia97]

Don’t see anything in the pictures, but from your description I believe you are talking about isopods. Most of them are completely harmless and are beneficial to your system. They have population booms depending on the detritus and algae in your system. If they do have a boom, they clean up your tank and become free food for your fish (some types are parasitic and will attach to fish, not so common tho)

 

[ISpeakForTheSeas]

Don’t see anything in the pictures, but from your description I believe you are talking about isopods. Most of them are completely harmless and are beneficial to your system. They have population booms depending on the detritus and algae in your system. If they do have a boom, they clean up your tank and become free food for your fish (some types are parasitic and will attach to fish, not so common tho)

It is indeed isopods (there are two visible in the first pic just to left of the center of the pic; the big one is visible in the same location in the second pic too).

OP, these are probably harmless, but you can verify that if they roll into a ball (conglobate) when disturbed (like a rolypoly or pill bug; if they do this, they're keepers) and/or by looking at their back half and tail on the topside and underside of the critters (vaulted/domed underside of the tail end is good even if it can't roll in a ball; flat underside is bad and can't roll in a ball).

Edit: Oh, and welcome to Reef2Reef!

 

[NeedAReef]

run your images thru Grok and see what it says?

 

[ISpeakForTheSeas]

run your images thru Grok and see what it says?

I've already addressed the ID, but with regards to using AI to help with ID'ing critters in our tanks:

AI is a fantastic tool, but also horribly deeply flawed at the moment (and possibly forever, though it will definitely get better), because it lacks the vetting capabilities of humans. For example, I primarily do hitchhiker ID's here, and sometimes I'll use Google Lens on an image to help with the ID process (I use it to help point me in the right general direction to help narrow down some ID's; sometimes it's helpful, and sometimes it's not - honestly, the more I learn, the less I use AI for direction, but sometimes it gets close enough with some of the results [almost never at the top] to help me figure out a taxonomic family, superfamily. etc.); it's a tool in my repertoire. However, trusting AI (Google Lens, in this case) to figure out the right ID would lead to incorrect identification pretty well every single time (the amount of times it tries to tell me that a crab, for example, is a whale shark or a cuttlefish is somewhat mind-boggling; and it's very confident in its replies, even going so far as to rebut my prompts to point it in the right direction and to tell me "No, this picture is not of a crab, it's of a whale shark"). AI is a tool to use to pursue the answers needed for our questions at this point, its answers are not actually the answers in the vast majority of cases (and not just due to the complexity of all the different circumstances/variables of each aquarium).


TLDR; trusting AI to be right is a major (likely unwise) leap of faith at this point, but AI is a good tool to get ideas or direction from in order to figure out an appropriate, correct (i.e. probably not AI) response through your own, human, vetting process and experience.

 

[NeedAReef]

never said to trust it, or much of the internet. If used correctly and prompted correctly it can do what a lot of people cannot, point you in the right direction.

 

[Nehemiah]

Don’t see anything in the pictures, but from your description I believe you are talking about isopods. Most of them are completely harmless and are beneficial to your system. They have population booms depending on the detritus and algae in your system. If they do have a boom, they clean up your tank and become free food for your fish (some types are parasitic and will attach to fish, not so common tho)

The tank is only about 4 gallons, so I wasn't planning on adding any fish. I suppose then it's fine then if they're bad isopods? but I just read that they bite people and I don't love that

 

[Nehemiah]

run your images thru Grok and see what it says?

I'm not sure what "Grok" is, but I tried google image search several times and it kept saying it was either a barnacle or a sea slug lol

 

[Nehemiah]

It is indeed isopods (there are two visible in the first pic just to left of the center of the pic; the big one is visible in the same location in the second pic too).

OP, these are probably harmless, but you can verify that if they roll into a ball (conglobate) when disturbed (like a rolypoly or pill bug; if they do this, they're keepers) and/or by looking at their back half and tail on the topside and underside of the critters (vaulted/domed underside of the tail end is good even if it can't roll in a ball; flat underside is bad and can't roll in a ball).

Edit: Oh, and welcome to Reef2Reef!

They've been getting larger and easier to see so a couple nights ago, I finally realized that some of them look very similar to my terrestrial dwarf isopods and then tried to ID them from diagrams of marine isopods online
but there are tons of them so I can't be sure.
The tank has TBS live rock and it does say on their website that their rock has parasitic isopod hitchhikers and at least one of the ones I saw after lights out looked very similar to their example.

Do you think they will die out eventually without any fish to host? or should I try to catch them?
Also, does anyone know if they prey on hermit crabs?
I read that they bite humans so ideally, I'd like to not have them. Is there a small fish that could eat them? but what fish could thrive in only 4 gallons?

It seems like research on them is scarce so I'm hoping that more experienced hobbyists might give me some advice.
Thank you for the help and the welcome!

 

[ISpeakForTheSeas]

They've been getting larger and easier to see so a couple nights ago, I finally realized that some of them look very similar to my terrestrial dwarf isopods and then tried to ID them from diagrams of marine isopods online
but there are tons of them so I can't be sure.
The tank has TBS live rock and it does say on their website that their rock has parasitic isopod hitchhikers and at least one of the ones I saw after lights out looked very similar to their example.

Do you think they will die out eventually without any fish to host? or should I try to catch them?
Also, does anyone know if they prey on hermit crabs?
I read that they bite humans so ideally, I'd like to not have them. Is there a small fish that could eat them? but what fish could thrive in only 4 gallons?

It seems like research on them is scarce so I'm hoping that more experienced hobbyists might give me some advice.
Thank you for the help and the welcome!

Yeah, learning to ID these can be a little tricky - I'll link the taxonomic key and stuff to help you figure it out if you want below.

Anyway, generally speaking, there are two superfamilies of marine isopods that can look superficially like this: Sphaeromatoidea (good guys that won't hurt you or your fish) and Cymothooidea (bad guys for our purposes). You can tell them apart by looking at the telson (technically a pleotelson) on the critter; domed (rounded) telson = good, flat/flattened telson = bad.

I can't tell for sure from your pics, but I would guess yours are Sphaeromatid Isopods (A.K.A. Seapills); you may have an easier timer telling in person than I can from pics though (side shot pics of the telson top and bottom would be useful for me).

The key (they do a simplified key for North American isopods, then a technical key for global isopods - I prefer the technical key):

American Isopod and Myriapod Group - ISOPODA

ISOPODA Latreille, 1817

www.americanisopodsmyriapods.com

Some resources to help figure out the key (the third link shows some examples of isopods with larger pleotelsons than the first link; the isopods you've got have a larger pleotelson, so looking at both links should give you a pretty good idea of what the pleotelson is even with some variation in size/shape):

And here are some pages with diagrams to figure out the morphology (I like the first and second ones for figuring out the general pieces/makeup of the bodies, but the third is very technically detailed):
Crustacea Glossary

Isopod Anatomy and Biology - Isopod Site

Isopod Anatomy Mature isopods have 7 pairs of walking legs that are pretty much the same. In Latin, "iso" means "same" or "equal" while pod means "foot". However, isopod mancae (babies) have only 6 pairs of legs in their initial instars. Isopods also have 2 pairs of antennae — one large pair and...

isopod.site

Untitled 1