Photosynthetically Induced Phosphate Precipitation

[Bilk]

I don't think we are only concerned with phos, it's just that phos and other certain elements can be precipitated out of solution on photosynthesising algae (it seems). Therefore we may be able to increase phos uptake / removal when required.

But maybe it's treating a symptom and not a cause. Yes alga utilize PO4, but they also utilize other nutrients. Now we need to understand which are preferred and which are readily available.

What happens to all the ammonium/NH4 that's created in the tank if the nitrosomonas bacteria population is depleted?

[Amphiprion]

Scrubbers only borrow bicarbonate. hydroxide is released and forms new bicarbonate on contact with Co2. You should have better growth with more alkalinity. Any loss is due to calcification or precipitation.

Duh, I can't believe I didn't think about this. I guess I should've at least thought about the equation.

[Bilk]

After reading a thread on RC about sand beds I'm totally confused and equally totally sure that trapped nutrients from detritus are the reason people experience problems with algae. Now the question is, which nutrient is the problem. Now if nitrates and phosphates read zero, there must be something else feeding the algae.

I love the look of sand but now I'm rethinking what I will do. I can still siphone it out

[Nick28]

Duh, I can't believe I didn't think about this. I guess I should've at least thought about the equation.

I don't want to hijack this thread but

I'm not really sold on the bubble rubbing thing I think flow is more useful for two reasons more bicarbonate and nutrient delivery + no light blockage from bubbles. My UAS just has a powerhead on it.

http://reefkeeping.com/issues/2006-10/rhf/index.php#21

This is a really good read on PH, photosynthesis, Co2 and algae.

[Garf]

Some pollutants in the form of elements and compounds that may be precipitated from water according to the present invention are indicated below:

Alkaline Earth Metals

Magnesium, Calcium, Strontium, Barium

Heavy Metals

Titanium, Chromium, Molybdenum, Nickel, Copper, Zinc, Vanadium, Mercury, Cadmium

Metals

Manganese, Iron, Cobalt, Lead, Boron, Aluminum

Prime Nutrients

Phosphorus, Sulfur, Carbon, Nitrogen

OK, so lots of this precipitation is definately good. however, there are a few on the list that are not tested for regularly. Are we sure that the essential elements that may be precipitated are delivered back into the aquarium by feeding and dosing etc, in high enough levels? A low level waterchange protocol would be advisable surely.

[Amphiprion]

Do all the elements in question necessarily need to be added back? What purpose do some of them serve? What concentrations are they present in artificial salt mixes to begin with? I think I'd rather take my chances without adding them back manually and do a very occasional small water change just in case--say a few times per year. I don't feel like spending that much on ridiculous quantities of salt mix in order to change water constantly like many do.

[Garf]

It may be that none of them are really important, other than the obvious ones like cal, mag etc. as there may be a certain input made by feeding etc. however a 1% monthly waterchange or so should guarantee its inclusion in the tank IMO.

Just a reminder that NONE OF THIS THREAD APPLIES to systems that maintains its scrubber water pH at below 8.3., at all times.

[Garf]

Screen clean today and I've got sparkly bits;

[xerophyte_nyc]

After reading a thread on RC about sand beds I'm totally confused and equally totally sure that trapped nutrients from detritus are the reason people experience problems with algae. Now the question is, which nutrient is the problem. Now if nitrates and phosphates read zero, there must be something else feeding the algae.

When you say phosphates are zero, what you really mean is inorganic phosphate is zero. Hobby testing kits don't analyze the organic P in the tank. Inorganic P can be consumed so quickly that you can't test for it. At low levels it is used up (by photosynthetic life) almost as quickly as it is made. Detritus has organic P within it, so when it lingers around in the tank, bacteria will metabolize it and create more inorganic P.

You are right about detritus being a big problem in our tanks. What makes it an even bigger problem is we can't measure it. It's easy in the ocean, nutrients get diluted and washed away. We can't do 100% water changes every few hours without plumbing your return line to the ocean.

[Garf]

A few results;

1] phos is definately going down
2] discolouration in the water has disappeared (I've always had a tint in the water, only visible under blues)

I was hoping to keep this next fact for a future testing but I feel it's too pertinent to this thread. Phosphate precipitates out at 9.9 pH (fact), dissolved organics flocculate into skimmable and trappable particles at pH 9.7 !!! (fact) So I don't think I'm over exaggerating when I say that running a scrubber with water around the 8.3 to 8.6 range (the rest of pH increase is at the photosynthetic surface) reduces phos levels and strangely dissolved organics, maybe even more effectively than a skimmer, especially in slower running water, ie with thicker screens. Any thoughts welcome.