Tisbe copepods?

[Levinson]

I have found a bloom of some tiny creatures in my tank today. There were thousands of them swimming around, mostly around one spot. I do have many tisbe copepods, apocyclops copepods, and some other copepods in the tank so I am used to seeing them every day, but these were much smaller and not something I am used to seeing. They also behaved differently. They were actively, constantly swimming around.
Video of them swimming around
At first, I thought maybe they are copepod nauplii, and I happened to see them just after a spawn but that didn't make sense to me either, since copepods that I know don't spawn together at once like this.
I decided to check with my microscope. They looked kinda like Tisbe but were not nauplii, at least they didn't look like any copepod nauplii that I know of.
Do you think they are just Tisbe copepods or something else? I put the links to the video below.

These are the links to the video.
Microscope Video 1
Microscope Video 2

 

[rayadog]

No expert so delve further. But really cool! What microscope do you have? This post specifically makes me want to invest.

Anyways, I agree they kinda look like Tisbe nauplii with an undeveloped caudal fork yet; an opinion not a fact. Do they all look like this or can you find different stages? Just curious.
They’re swimming and they look like underdeveloped Tisbe sp. to me so checks nauplii box for now

 

[Levinson]

No expert so delve further. But really cool! What microscope do you have? This post specifically makes me want to invest.

Anyways, I agree they kinda look like Tisbe nauplii with an undeveloped caudal fork yet; an opinion not a fact. Do they all look like this or can you find different stages? Just curious.
They’re swimming and they look like underdeveloped Tisbe sp. to me so checks nauplii box for now

I used Swift sw150, it's just a cheap microscope. Not that I don't like the microscope, I would have invested a little more and got a better one if I had known more back then.
They did't look like Tisbe nauplii in their early stages I found online. This swarm of copepods(?) were seen on one spot and it is no longer there now. They all looked the same. If they were Tisbe, they looked somewhat, but not fully grown. I thought it was odd that Tisbe at such developmental stage would all get together in one spot at one time for a while then go on their way.
These behaved very differently from other adult harpacticoid copepods in the tank. Much more active (as you can see in the video) and they apppeared to be swimming rather then crawling.

 

[rayadog]

Yea that was weird but idk what the set up is like; flow, heat, light, etc. I figured they were nauplii because they were free swimming, I thought they settle to mostly crawling as adults.

What else do you know you have in the tank?

 

[Levinson]

Yea that was weird but idk what the set up is like; flow, heat, light, etc. I figured they were nauplii because they were free swimming, I thought they settle to mostly crawling as adults.

What else do you know you have in the tank?

Yeah that was weired. I haven't seen them since. My tank is crustacean dominant tank with shrimps, crabs, hermit crabs, etc. No coral or fish.

 

[Levinson]

The same thing happened again tonight (and a few times before that as well).
I suddenly find many tens of thousands of them little guys at night in the tank. These little guys aren't normally around which means something is spawning I just don't know what. I personally think Tisbe is unlikely because there are far too many of them when they spawn.
These guys are attracted to light btw.

 

[Levinson]

My current guess would be they are isopod or amphipod nauplii.
I can't seem to find any decent images of them online though.

 

[Levinson]

I still get the spawn regularly. This one time, I tried to put them into a plastic cup with live phyto to see if they would grow, but they all died after a few days. Still no clue what they are.
I took some video with a USB microscope.

Video 1
Video 2