Reef Chemistry Question of the Day #298: Where are those trace elements coming from?

[Randy Holmes-Farley]

Reef Chemistry Question of the Day 298

We all know that organisms from bacteria to whales require many different trace elements for the biochemical processes of life.

One of the things we don't always have a good handle on in a reef tank is where they are coming from and where they are going.

It is common for folks to assume that water changes are an important way that trace elements get into a reef tank.

But when not dosing them, are water changes the main way?

There have been studies of the relative contribution of trace elements from foods and water changes (e.g., by Ron Shimek):

https://reefkeeping.com/issues/2002-04/rs/feature/index.php

but some aspects of those results (and the data they are derived from) make me skeptical of some of the results.

So let's use more widely recognized sorts of public data.

Here's the question.

Which adds more iron to a 100 L reef tank that is completely depleted in iron:

1. A 100% water change with natural seawater, which we will assume for this purpose has a concentration of 0.5 nM or 28 ng/L = 0.028 ug/L
2. 1 medium shrimp (size 41-60/pound)
3. Nori sheet 7" x 8"
4. 1 whole sardine (2-2/3" x 1/2" x 1/4")

Note that the question is not asking about bioavailability or even how much of the iron ends up in the water after some period of time, which would be complicated for all of the choices, but just how much total iron enters the aquarium via these means.

Feel free to guess.

Good luck!

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[KrisReef]

Sardines have a whale of a lot of iron in them!
Shrimp do too, about the same as a water change.

I think Nori is better for Iodine additions, and a water change is inferior to 40/pounds of shrimp (what I read initially )

So I would not eat them myself but Sardines are an excellent choice for Iron supplements for a reef.

 

[jda]

I am guessing a Sardine since I am not good with them maths and I do some nori, shrimp and change water and I still have to dose iron... not that even a whole sardine might be enough.

Looks like nori has a lot at first glance, but they all give the nutrition in 100g amounts... which is a lot of nori.

 

[Reefahholic]

Just dose it. Simple, Precise, Done.

 

[Miami Reef]

Sardine?

 

[Raul-7]

I'm going to guess Nori simply because iron plays such a crucial role in plant photosynthesis.

 

[Reefahholic]

Sardine?

Throw you a couple Sardines in the system. Hehe

 

[taricha]

My guess is...

3. Nori sheet.
Mama always said eat your veggies.

 

[PeterEde]

Nori the spinach of the sea. Spinach is very high in iron

 

[PeterEde]

Since moving from 120 to 425 my Foxface and Lemonpeel have gone off the nori.
At least my PO4 wont climb

 

[Randy Holmes-Farley]

And the answer is...

Which adds more iron to a 100 L reef tank that is completely depleted in iron:

1. A 100% water change with natural seawater, which we will assume for this purpose has a concentration of 0.5 nM or 28 ng/L = 0.028 ug/L
2. 1 medium shrimp (size 41-60/pound)
3. Nori sheet 7" x 8"
4. 1 whole sardine (2-2/3" x 1/2" x 1/4")


The values quoted vary a lot, but the best I can come up with is:

4>3>2>>1

sardine has most
nori is second
shrimp is third
and even a 100% water change is way, way below all of these.


Note these are all quite close to one another. Let's look at each in detail:

1. A 100% water change with natural seawater, which we will assume for this purpose has a concentration of 0.5 nM or 28 ng/L = 0.028 ug/L

Clearly, that 100% water change adds 0.028 ug/L x 100 L = 2.8 ug

2. Values vary a bit by web site and cooked vs raw, but are typically in the ballpark of 0.4 mg per 112 g of raw shrimp. A medium shrimp is usually defined as 41 to 50 per pound. Let's say, 45 per pound, or 10 g/shrimp. Thus, 1 medium shrimp contains about 10g/112g x 0.4 mg = 0.036 mg, or 36 ug.

Quick Guide: Shrimp Sizes and Counts Per Pound

Colossal shrimp? Large shrimp? 26/30? What does it all mean? Learn how to decipher shrimp size labels, determine the count you need for your recipe, and get cooking inspo in this reference guide.

stripedspatula.com

Medium raw shrimp nutrition facts and analysis.

www.nutritionvalue.org

3. Values vary a lot by web site. A typical 7 x 8 nori sheet weighs about 100 g per package / 30 sheets per 3.3 g.

Nori Sheets, 100 g

Nori sheets are a convenient way to make sure your tangs, angelfish, wrasses, surgeonfish, blennies and butterflyfish fish are getting the vegetable proteins, minerals and vitamins they require. Not for human consumption.

www.brineshrimpdirect.com

Iron at the site below is 11.4 mg iron per 100 g nori, or 0.34 mg/sheet = 340 ug/sheet.

NUTRITION | Mikuniya of Nori

mikuniya-nori.jp

Iron at the site below is 1.8 mg iron per 100 g nori, or 0.06 mg/sheet = 60 ug/sheet.

A third site says 0.2 mg/10 g = 200 ug/sheet

Seaweed Nutrition Facts and Health Benefits

Two tablespoons of wakame (10g) provides 4.5 calories, 0.3g protein, and 0g fat. Seaweed benefits include providing magnesium, calcium, and iron.

www.verywellfit.com

We'll assume an average of about 200 ug iron / sheet

4. Sardines contain an average of 2.9 mg of iron per 100 grams.

https://www.dailyiron.net/sardine/

A typical small 2" sardine (as might be fed to a reef tank) weighs 15 g.

Nutritionix

www.nutritionix.com

Thus, a small sardine contains about 0.44 mg of iron = 440 ug of iron.

Thanks everyone for playing!

Happy Reefing!