Diatoms help! Ever since carbon dosing...

[mahi03]

Ever since I started carbon dosing (started off vodka only, and now doing DIY Nopox), I started getting diatoms. I clean my glass in the AM and by evening I have a light layer with some heavier spots. Tank is two years old, filled with corraline, a little GHA. I do have a very heavy bioload from overcroweded fish stock.

Besides zero acro growth, tank was relatively algae free for many months. 4 months ago, I started carbon dosing to bring nutrients down from tested levels of NO3 at 120 and PO4 at 1.2, as my acros weren't growing. With carbon dosing, NO3 has now been in the 12-16 range for the last 2-3 months, and with LC/GFO, PO4 fluctuates between 0.1-0.2

But the diatoms appeared and remain heavy. I now clean glass twice a day.

I've changed the DI cartridge a couple of times and that doesn't seem to help. I've changed the vodka brand in case the original vodka water may have had silicates. Before I go buying another cannister and installing a silicatebuster, or some other $$$ measures, wanted to seek advice on what may be causing this and how I might be able to mitigate the issue?

Volume: 80g DT, 30g sump
Alk: 8.1
Ca: 460
Mg: 1380
NO3: 14
PO4: 0.10
Lighting: 12-hour cycle with 1-hour ramp-up and down, this hasn't changed in over a year
RODI: BRS 5-stage, all new cartridges
Flow: I was running 2 mp40's but recently switched to 2 dcw-120 gyre style pumps. There is plenty of flow in the tank with very minimal dead spots.

Alk/Ca/Mg have been stable. Most coral seem ok, but have experienced some LPS/SPS losses over the past month. I run a small fuge with chaeto.

 

[Randy Holmes-Farley]

What makes you think they are diatoms? What color are they?

Organics do not typically spur diatoms, but do spur other things, such as cyano.

 

[mahi03]

What makes you think they are diatoms? What color are they?

Organics do not typically spur diatoms, but do spur other things, such as cyano.

dark-ish brown dusting/film on glass.

I don't have the benefit of a microscope, but I'm certain it's not cyano, as I had a bout with cyano a year ago. It is not stringy, and there are no air bubbles. Oddly, it also sticks primarily to glass, and not on sand/rock.

 

[mahi03]

Scientifically, I understand the addition of organics should not spur diatoms, and that they're typically a function of silicates in water. I had diatoms for a short period during the tank's ugly phase some 18+ months ago, but if I recall at the time it was also on the sand.

Anecdotally, the diatoms appeared with the drop in NO3 and PO4 that coincided with the dosing. Is there a brown dust/film "algae" that covers glass that are not diatoms?

If unlikely, would another DI cannister with a specific silicate remover be helpful? I pause before doing this, as I had many many months of rarely needing to clean glass, so I'm somewhat doubful it's due to the already relatively clean San Francisco water.