what is this stuff?

So our tank is FOWLR, but I would like to change that and get some soft corals (and get rid of hoaky plastic crap). We have some sort of algae which is growing largely due to our high nitrates (between 10~15) which we have been waging war on by doing 50% water changes and is down from a high of 30. Our tank took almost 4 months to cycle and in doing so got a lot of nitrate built up before all the ammonia went away completely.

my question is three fold;

-first, what is this stuff ?

-How can we get rid of the nitrate completely ? We have thought about taking LR and putting it in 5 gallon containers with a few gallons, and then completely emptying cleaning the tank and starting out with 75% new water.

- We recently got a blue legged hermit crab, and wherever he goes he leaves the LR whitish behind him, what is he doing and what is causing this ? (far left rock)

 

Looks like cyanobacteria. It comes from having too much phosphate and nitrate in the system. Increased flow helps with keeping it from forming as easily. You will need to get granulated ferric oxide to help reduce the phosphates and it helps with nitrates a little also. If you are using tap water then you will want to switch to RO/DI water. You would need to double your live rock, you can do this by buying dry base rock and letting it become colonized by bacteria. Change your substrate to sand will help in reducing your nitrate to nitrogen. You will need to siphon the substrate aggressively to keep detritus from forming nitrate factories in it. Cut back on your feeding, clean your filtration thoroughly often and change media every two weeks.

Your hermit is eating the algae and cyano from the rock. Increase the number of hermits and snails in your tank to combat detritus and algae.

 

Looks like cyanobacteria.
The crab is leaving white spots because he's picking it off the rocks LOL.
Crushed coral substrate isn't helping with the nitrates.

We'd need a lot more info about your tank to help more.

Tank size
Tank age
How it was cycled
Water source
Filtration type (filter make/model, skimmer, lights, etc.)
Sump/refugium or not
Inhabitants (crabs, fish, snails, corals, etc.)
Water parameters (SG, ammonia, nitrite, nitrate, pH, and anything else you check for).
What, how much, and how often you feed.
Intentions for the tank (fish only, fish only with live rock, reef)

If you do take the rock out, I'd take that opportunity to replace the crushed coral with sand.

 

I took too long to type LOL.

 

No I had a head start. All great requests on your part.

 

I get premixed salt water from LFS who sold us fish etc. It is supposed to be RO. We were planning on swapping out the substrate to sand. we currently have 4 fish in the tank, and feed them 1 half block of mysis shrimp each day.

 

29 gallon
8 months
cycled by placing a lone dead deli shrimp in tank and monitoring ammonia
no sump
aqueon medium filer
3 snails, 1 blue legged hermit crab
2 blue damsels, 2 clowns
SG 1.024, Ammonia 0 nitrates 10~15, ph 8.0
half block mysis shrimp daily
reef

 

Definitely look into a RODI unit if you want to have a reef. Rinse your mysis before putting it in the tank. You can probably cut back to a quarter of a cube with your fish.

How much circulation to you have in gallon per hour? If the tank is only going to be fish only then 10 to 20 times the tank's volume per hour for circulation is good.
If you are going to go ref then you will want 20 to 40 times per your for a softies/LPS reef and 50+ for SPS.

Definitely increase your clean up crew. Probably at least 10 of each snail and hermit minimum. Go to ReefCleaners.org | Clean Up Crews and Macro Algae - Home, one of our sponsors, to get a better recommendation.

 

You really should consider a protein skimmer.

 

What ^^ he ^^ said!
Try testing the water you get from the LFS sometime and see what kind of readings you get. We got some from a place when we needed more than we had made and found it had 10 ppm nitrates in it!

If you're going reef, also look into getting a skimmer.