diatoms cyano, dino's or other??

[DS5000]

new 50gal RS 170, 2.5months in, mixed reef with a few fish.
I noticed brownish algae about 2wks ago that looked like diatoms. They went away after about 1.5wks. I used phosguard, and bottomed out my phos to zero. My tank was pristine for 3 days, and then brownish/green algae starting to grow again on rocks, sand and glass. I am not sure if my current algae is expected cyano, recurrent diatoms, or now dino's due to phos issue. The algae color looks the same, but now i notice algae 'strands'/'fronds' (not sure of the name) growing.

salinity 35ppm
nitrates 2-5
phos 0 ---- I removed the phosguard 12 days ago, although my phos continues to be zero despite multiple readings by hanna checker, and nyos testing kit;
alk 8.5
pH 8.2

was feeding pellets food 1x day with mysis 2x week for my 4 fish (clowns x2, cardinal, wrasse) before all this
i have 3 trochus, 3 nassarius, and 1 emerald crab
some coral frags - they all seem to be doing well
running skimmer, carbon, filter floss
RODI

not sure how to
1. diagnosis my problem
2. treat it
-is it brown cyano, and the next stage in my new tank
-is in dinos due to the phos? - I dont notice any bubbles, or a slime/stringy consistently
-is it recurrent diaotoms

I have started to feed now 2x day pellets, and mysis every day to try and increase the phos. I could dose phos?

pls help! Thank you !!

 

[biophilia]

It looks like regular old green film algae to me. Maybe some blue-green cyano on the sandbed or else diatoms. Either way, don't worry too much about chasing numbers. The tank is new enough that algae blooms like this are inevitable. The phosphate is reading zero because it's in flux and being used by the algae, not because there's actually zero phosphate present in the system. It's not necessary or helpful to dose phosphate.

IMO the easiest way to deal with the algae is to add more herbivores. Except for really extreme examples, excess algae is usually just a function of a lack of grazing pressure.

Consider adding another ~10 trochus, maybe an urchin or two, and possibly some hermits, and giving it a month or two before chasing numbers.

 

[DS5000]

thx biophillia
apprciate it
i didnt think to consider low phosphate due to algae consumption of it. Ill continue to monitor, and see how it goes.

 

[GoVols]

Consider adding another ~10 trochus, maybe an urchin or two, and possibly some hermits, and giving it a month or two before chasing numbers.

+1

along with a mixture of pod species and Algaenbarns OceanMagik Phytoplankton.

 

[DS5000]

for the urchin - what kind is good for algae remover?