Another what are these question

[tjs1200]

Two days ago our tank crashed and we lost all of our small friends, the ammonia level last night was .25 and nitrites were 37 ppb. With the tank cleaning, I found two creatures that I can't identify and one brownish stringy algae, I have no idea where the ammonia came from, the tank is about 6 months old. Thanks for the assistance in advance.

 

[EeyoreIsMySpiritAnimal]

Those are hair worms. Harmless detritivores.

 

[EeyoreIsMySpiritAnimal]

Fwiw, if you were using API to test ammonia, a reading of 0.25 can be considered 0 in an established tank since that test (and others) measures total ammonia (ammonia plus ammonium), not just free ammonia which is the bad one.
And there is no need to test nitrites; aside from making nitrate tests results wrong, there's really no ill effect of nitrites in saltwater... freshwater is another story.

 

[tjs1200]

That is the test kit I was using thank you

 

[EeyoreIsMySpiritAnimal]

That is the test kit I was using thank you

If the water quality wasn't the issue, what else might have caused the livestock loss?

 

[tjs1200]

We added some microalgae which is all we added, purchased at the LFS

 

[ISpeakForTheSeas]

We added some microalgae which is all we added, purchased at the LFS

Just to clarify here, the pic you shared is a macroalgae (looks like Caulerpa chemnitzia var. turbinata; I'd guess it was sold as Caulerpa racemosa) - microalgae species are microscopic, and the term is used pretty broadly to include things like phytoplankton, cyanobacteria, dinoflagellates, etc.

Anyway, I'd personally assume your livestock losses were caused by disease (which may or may not have been brought in with the Caulerpa), especially if you only lost the fish in the tank.

 

[Tired]

Ah, neat, hair worms. Also known as spaghetti worms, some of them can get fairly large (I have one with 6"+ feelers), but all are harmless, potentially useful detritivores. That stringy algae looks a bit like more of them, actually.

Did the fish show any symptoms? Gasping, flashing, swimming into the flow, lethargy?

 

[tjs1200]

They were swimming in the flow prior to showing signs of lethargy and then hiding and dying.

I suspect that if the water wasn't the problem and the only time we had a issue is when we brought the microalgae in the tank, this probably btought disease from the micro algae as suggested above.

I think The hair worms were brought in on the micro algae.

 

[Tired]

When did you add the macroalgae? That seems pretty fast for a disease to have taken hold just from that, if it was recent.

Swimming in the flow can mean several things, but velvet is fairly likely. The good news is, velvet can be eliminated from your tank by a fallow period; it'll die off eventually if you have no fish for it to live on. Though you'll have to look up how long that fallow period should be, as I don't recall off the top of my head.

 

[ISpeakForTheSeas]

Though you'll have to look up how long that fallow period should be, as I don't recall off the top of my head.

45 days at 81F minimum; 60-76 is suggested, especially if at lower temps.

 

[tjs1200]

The micro algae was added about 3 to 4 weeks ago thank you for the information

 

[Tired]

Yeah, all the fish dying more or less at once a few weeks after a newly introduced wet substance sounds like disease. That's why folks who go the full quarantine route opt to QT non-fish for long enough to allow most affixed diseases to die off.

 

[tjs1200]

Lesson learned