YoYo Nitrate Level

[bertoni]

Ah, that's interesting. How big are the mussels? Is 5-10g about right?

 

[Dan_P]

Ah, that's interesting. How big are the mussels? Is 5-10g about right?

I will get a number.

 

[Dan_P]

Ah, that's interesting. How big are the mussels? Is 5-10g about right?

1 Mussel

Total wt - 20 g

Rinsed meat with tap water and patted dry with paper towel - 6.5 g
Rinsed and patted dry shell - 10.5 g

Meat cut up, rinsed, patted dry - 5.3 g

So, I was feeding 10 g of mussel before cutting back to 5 g. Also, it seems that I wash off 4.2 g of "œjuice" from each clam.

 

[taricha]

1 Mussel



Total wt - 20 g



Rinsed meat with tap water and patted dry with paper towel - 6.5 g

Rinsed and patted dry shell - 10.5 g



Meat cut up, rinsed, patted dry - 5.3 g



So, I was feeding 10 g of mussel before cutting back to 5 g. Also, it seems that I wash off 4.2 g of "œjuice" from each clam.

I did the following in my head today.



An increase of 0.5 ppm NO3 in a 185 L system corresponds to adding ~93 mg of NO3. This amount of NO3 corresponds to about 23 mg of N. If biomass contains 7% nitrogen, then roughly 300 mg was digested, maybe more if some N was assimilated by the organism. But this is dry weight. Assuming 80% water content, the ballpark biomass digested is 1.5 g. I haven't weighed the washed mussel meat yet to see how the two numbers compare. If the mussel meat was 5-10 g, I would be impressed that this simple calculation was within an order of magnitude.

According to http://www.fao.org/wairdocs/tan/x5916e/x5916e01.htm
You were pretty spot on. They list mussels as 80-84% moisture, and 8.9-11.7% protein.

 

[bertoni]

That does seem very close.

 

[Dan_P]

That does seem very close.

Coincidence maybe.

Another coincident I will report on is the amount of carbon dosed to consume nitrate in my small scale experiments. I need to do a couple more experiments though.

I have wondered recently whether we could predict the required amount of carbon to reduce a nitrate level or alternatively, could you run a small scale experiment with a sample of tank water where you aggressively add carbon over a few day period until the nitrate is consumed and empirically determine the amount of carbon required. This is turning out to be an interesting subject.

 

[bertoni]

The amount of nitrate consumed per gram of organic carbon would be interesting, even if it's only a few data points for one tank. I wonder how much it'd vary. Maybe not a lot.

 

[taricha]

10g mussel at 8.9-11.7% (call it 10%) protein is 1000mg Protein. 16% N content of protein means 160 mg Nitrogen or 700 mg NO3 equivalent.
In a 185L system that works out to an input of 3.8 ppm NO3.

So looks like less than 1/4th of the N input actually shows up as testable NO3 in the water at any one time. The rest hangs out in various digestive tracts and is slowly released as NO3 is taken up by algae etc.