Bloom of something "twitchy?"

[pacificdiver]

I have a 150 gallon system that's been up for about 6 weeks - just started getting the brown stuff in patches on the substrate. I turned the tank light on this morning and to my surprise, there were thousands of larvae of some sort, twitching happily in the water column. They were extremely tiny, and all I could see was that one end was more massive than the other, and they twitched their "tails" to move. Can frozen mysis bring larvae into the tank? The 7 small fish in the tank were happily picking them off for the better part of an hour, until they were pretty much gone. Can someone tell me what these things could have been? Would love to have a scope to take a look at one, but no such equipment. I'm not worried at all about it (unless I should be?), but just curious what they could have been.

System
Ocean Direct substrate
140 lbs Life Rock
3 Green Chromis / 2 ocelaris / yellow wrasse / Jester Goby / 10 hermits
Fed frozen mysis and small pellets

Anyone have any advice on what this could likely have been?

 

[AlSimmons]

What you were seeing may have been hermit crab larvae.

 

[gone fishin]

I would not think anything in the frozen mysis would survive but, stranger things have happened. With out a pic it would be really hard to tell. Maybe call up some copepod pics to compare. Have you added any cheato?

 

[pacificdiver]

What you were seeing may have been hermit crab larvae.

Hmmm....I just added the 10 hermits the day before, so that would make a lot of sense. Thanks for the feedback to both of you!

 

[AlSimmons]

Did you use any live rock? Mysid shrimp are known to hitchhike their way into our aquariums sometimes, but they don't necessarily twitch. They have more of a flight plan in mind when they move about.

 

[pisanoal]

Sounds like a copepod bloom.

 

[Rybren]

Probably Mysids.

What really worries me is that you have 7 fish in a 6-week old tank. Please don't add more fish for the time being. The tank needs to mature more.