Diatom bloom in somewhat established tank?

chrissymoon · Nov 24, 2021

Currently have a 125g tank that was previously running at former owners home for 2+ years. Basically just transferred the entire tank to my house (minus the water).

Two weeks ago, nitrates were sky high (150ppm). I dosed the tank with seachem prime because that’s all I had on hand. I did a 75% water change and attempted to sift the sand (BIG MISTAKE). I didn’t know you’re not supposed to touch the sand!! (first saltwater tank).

now the tank is full of this brown crap plus stringy looking algae all over the rock! I don’t know what to do. I bought 2 emerald crabs, 4 nassarius snails and a sand sifting starfish. The tank hasn’t improved at all. I only have 4 clownfish, one lemon damsel, one blue velvet damsel, one neon dottyback and one lawnmower blenny plus about 4 hermit crabs.

I tested the water two days ago and the values were as followed:
pH - 8.2
Ammonia - 0
Nitrate ~ 10
Nitrite - 0
Salinity - 1.027
Temperature - 79.8

what can I do? Is this normal? I don’t want to add anything else in the tank for fear of it dying because something is wrong with the tank.

blaxsun · Nov 25, 2021

What are you running for filtration? If you're using standard filter socks you could change those out every day for the next week to help.

Not that it's mission critical, but you should also check your phosphates.

With respect to the sand, if you're going to clean again it you'll need to invest in one of those substrate vacuums (you don't want to just stir it up as, well - you see what can happen).

You can try Vibrant (I'd dose every week) and a UV will help long-term with algae. Definitely hold off adding anything else until you get a handle on your nitrates, phosphates and algae issues.

Dan_P · Nov 25, 2021

chrissymoon said:
Currently have a 125g tank that was previously running at former owners home for 2+ years. Basically just transferred the entire tank to my house (minus the water).

Two weeks ago, nitrates were sky high (150ppm). I dosed the tank with seachem prime because that’s all I had on hand. I did a 75% water change and attempted to sift the sand (BIG MISTAKE). I didn’t know you’re not supposed to touch the sand!! (first saltwater tank).

now the tank is full of this brown crap plus stringy looking algae all over the rock! I don’t know what to do. I bought 2 emerald crabs, 4 nassarius snails and a sand sifting starfish. The tank hasn’t improved at all. I only have 4 clownfish, one lemon damsel, one blue velvet damsel, one neon dottyback and one lawnmower blenny plus about 4 hermit crabs.

I tested the water two days ago and the values were as followed:
pH - 8.2
Ammonia - 0
Nitrate ~ 10
Nitrite - 0
Salinity - 1.027
Temperature - 79.8

what can I do? Is this normal? I don’t want to add anything else in the tank for fear of it dying because something is wrong with the tank.

The question that I can comment on is whether what happened is normal. The event is certainly likely to happen when the biofilm of the entire system is severely disturbed. What was once an established waste disposal system is now dying and beginning to reestablish itself. This could take awhile. Diatoms, dinoflagellates and cyanobacteria may make an appearance. I agree with your approach about not adding anything to the system for now.