Any one know what these are?

[JayCow]

I have these little guys gliding all over glass any ideas?

 

[WalkerLovesTheOcean]

Most likely flatworms, I would get rid of them ASAP.

 

[JayCow]

They move pretty fast

 

[EeyoreIsMySpiritAnimal]

Flatworms. How long has the tank been set up, and what fish do you have?

 

[JayCow]

I have these little guys gliding all over glass any ideas?

Flatworms. How long has the tank been set up, and what fish do you have?

It's a year and half old and fish recently died. Just added a mimic tang.

 

[WalkerLovesTheOcean]

It's a year and a half old and fish recently died. Just added a mimic tang.

Flatworms, when they die do release a toxin into the water column, though I don't think this is what killed your fish, it is a possibility.

So just be careful when trying to get rid of them.

 

[EeyoreIsMySpiritAnimal]

Ok, they're probably just growing in numbers without any natural predators. Do you have coral? They can possibly affect them but only in large numbers...

From the interwebs:

Rust Brown Flatworm

The Rust Brown Flatworm (Convolutriloba retrogemma) is the most common flatworm found in home marine aquariums. It is rust brown to tan in color with a bright red dot about three-quarters of the way down its body and will reach a size of about 1/4". They are oval and somewhat elongated with two tail-like appendages. It reproduces rapidly in nutrient-rich marine aquariums. In high concentrations on a coral's surface, these flatworms can actually keep adequate light from reaching the corals, effectively starving the coral.

 

[JayCow]

Flatworms, when they die do release a toxin into the water column, though I don't think this is what killed your fish, it is a possibility.

So just be careful when trying to get rid of them.

No fish had an ich situation.

 

[JayCow]

Ok, they're probably just growing in numbers without any natural predators. Do you have coral? They can possibly affect them but only in large numbers...

From the interwebs:

Rust Brown Flatworm

The Rust Brown Flatworm (Convolutriloba retrogemma) is the most common flatworm found in home marine aquariums. It is rust brown to tan in color with a bright red dot about three-quarters of the way down its body and will reach a size of about 1/4". They are oval and somewhat elongated with two tail-like appendages. It reproduces rapidly in nutrient-rich marine aquariums. In high concentrations on a coral's surface, these flatworms can actually keep adequate light from reaching the corals, effectively starving the coral.

That does seem to match the bill here

 

[EeyoreIsMySpiritAnimal]

Flatworms: The Good, the Bad, and the Pretty Terrifying--Part 2 and Conclusion

How to manage flatworms in the saltwater aquarium. There is a discussion of types of flatworms, types of remedies, and when to use them.

www.reef2reef.com

 

[EeyoreIsMySpiritAnimal]

Flatworms: The Good, the Bad, and the Pretty Terrifying, Part 1

A description and discussion of marine aquarium flatworms and what to do about them.

www.reef2reef.com