Sizing a scrubber based on feeding (guideline review)

Hello again,

I am looking at the math given in the guidelines for sizing the scrubber and it doesn't seem to balance out when comparing dry feed to frozen at all. Maybe I am not visualizing what size a "Frozen Cube" is correctly, so please let me know what you think of these calculations. I manufacture foods, so I am always looking at things on a "dry matter basis" because that is how to compare apples to apples so to speak.

Frozen food cubes are typically 85%-90% moisture. FACT
My gel foods when hydrated according to the directions are 85%-90% moisture...

So we can compare apples to apples in this regard.

When I think if a "frozen cube" of fish food, I am picturing a cube the size that they are packaged pre frozen and ready to pop out..... hikari for example. This cube is about 1/2" square.

Yet, the recommendations show that 1 "frozen cube" is the equivalent of 2.8 grams of dry pellets using a two sided screen.

If I take 2.8 ounces of dry feed and hydrate it the same as a frozen or gel food, I end up with a cube that is approx 25 grams, or the size of a large ice cube made in a typical freezer tray.

That is a LOT bigger than the frozen cube I am picturing.

Can someone clarify the size of a "frozen cube" by weighing it. I am guessing it is probably five grams.

So either the equivalents being used for dry food are way off, or the size of the cube you are talking about is way off in my head.

At the end of the day it is aboutcomparing the amount of nutrients on a dry matter basis, and beyond that, the nutrient density of the different foods can also play a part.

To figure the amount of dry feed by weight in a frozen cube, just weigh your average cube and multipy it by .125.

If a frozen cube weighs 5 grams, then in this example, we are really only looking at about 625mg or .625 grams of dry feed...... and comparing it to 2.8 grams of pellets as equivalent in the guidelines.

Cheers, Allen

1 frozen cube per day (2-sided screen), or
1/2 frozen cube per day (1-sided screen), or
10 pinches of flake food per day (2-sided screen), or
5 pinches of flake food per day (1-sided screen), or
10 square inches (60 sq cm) of nori per day (2-sided screen), or
5 square inches (30 sq cm) of nori per day (1-sided screen), or
0.1 dry ounce (2.8 grams) of pellet food per day (2-sided screen), or
0.05 dry ounce (1.4 grams) of pellet food per day (1-sided screen)

 

Hi Bud,

If you look at whole live fish, squid, shrimp, plants, they all are around 80% water, so mash it up and you will find that if you add about 5% water, this gives you a workable slurry. Beyond that, nutrient density is the x factor..... for example, if you have one food that is 25% protein and 5% fat, and another that is 50% protein and 10% fat, you are approximately adding twice as many nutrients to the equation. Another x factor is the amount of organic/inorganic phosphates in the diet... if you have two feeds with the same protein and fat, but one has twice as much phosphorous in it, this will also have a major effect on the system. In tanks with a lot of feeding, this is probably why some people report nitrate is the limiting factor, while others report phosphates are limiting.

You could have a food that is 40% protein and 2% phosphorous (those that use pyproduct fish meal) and another that is 40% protein and 1% phosphorous (one that uses whole fish meal) and you are going to be putting two competely different loads on the system.

To start, Dry Matter Basis (DMB) is definitely THE way to level the playing field as much as possible. My previous example clearly shows that the recommended comparisons are off by as much as 5X

I would recommend that you (I can help) revisit this and base the recommendations on converting everything to something like per gram of dry feed. (sub qualifying that with an "average" feed nutrient density of 40% protein, 8% fat, and 1.5% phosphorous (the average density of most good feeds)

Looking at the numbers, you might say the L2 is good for . gram per day feed (DMB)
Which would be the same weight of pellets, flakes, or powder.
Or this would be a frozen/gel cube that weighed approx 3 grams (which is probably what a "cube" weighs...

Given the cube size is correct, if the food was the same nutrient density, .5 grams of dry feed would equal a cube.

which is WAY off from the guidelines of 2.8 grams dry feed equals one cube...... The guidelines look like they are just comparing dry and frozen on an equal weight basis and not considering that the water content is "empty weight"

Cheers, Allen

PS. I make a small line of high quality gel food premixes. They have been targeted primarily at the Freshwater market but some of the formulas are quite suitable for saltwater species. I have several institutions and hobbyists helping me develop some salt specific formulas and will relabel a few of the current formulas for salt.

I didn't come on here to plug my foods but since you asked about them, I will take advantage of the opportunity

Here are some videos a friend/dealer came up with introducing the line.

[video=youtube;IXmZ4kWb3X4]https://www.youtube.com/watch?v=IXmZ4kWb3X4&list=PLby5yv00rWaUzedmKeoIgzVO aUMEwOn9h[/video]

 

Actually it is pretty simple......

Hikari lists 86% moisture for most of their frozen products. here is an example http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=13937

Ocean nutrition lists 85% moisture for theirs.

I use 85% for mine....

So all you need to do is go to the freezer and weigh some of the cubes you have..... or get a friend or someone on here to do it...

Weigh a dozen or so and get an average. maybe do this for ocean nutrition/hikari and see how close they are.....

Then just take that average weight and multiply it by .15 and you have the DMB food weight of the cubes.

We can round quite a bit and still be a WAY more accurate than the current guideline you are using....

if a cube weighs 3 grams, then we can call that .5 grams of dry food.... so a "2 cube a day scrubber" would nicely convert to a 1 gram a day (DMB) scrubber

Most frozen whole animal foods are 50-60% protein and 10-15%fat..... total phosphorous will vary but 1% is likely a good average.

So to further quantify the guideline you could say something like "based on an average protein/fat/total phosphorous level of 50/10/1"

This would at least establish a pretty good baseline.

On another note, My "Spawn and Grow" formula is currently being used and tested for conditioning broodstock and raising saltwater fry of clowns and other species at the University of Florida Aquaculture Lab and by several hobbyist breeders.

Send me a scrubber and I can do some controlled studies

Allen

 

I have no clue how you make your foods, but if you want to spend the time, it is pretty easy to get a fairly good estimate of the water content in your DIY mix if you have a scale handy.

1. Make up a batch of your food just the way you feed it, and weigh out a portion that weighs exactly 100 grams.

2. Take that 100 grams and put it in a heat stable lightweight shallow dish or pan. You could even just bend something up out of aluminum foil.

3. Put the food in the dish/pan and weigh it again so you have a total weight of the food and the container together.

4. spread out the food in the pan so it is as shallow as possible.

5. put it in the oven at around 120-140 degrees.

6. Pull it out every hour and weigh the whole thing, comparing it to your original weight of the food and container combined. (it will start getting lighter)

7. Do this once every hour, or half hour, until your weight isn't changing.

8. Once it doesn't get lighter, you have evaporated off all the moisture, so you are left with a "dry" version of your mix.

9. The amount of dry food you have left (not including the weight of the container), is equal to your dry weight percentage.. (if you have 25 grams left, then 25/100 = 25% solids and 75% water.....

10. Repeat whole process to confirm!

Of course the nutrient/phosphorous density of your mix is going to be something you will have to guesstimate based on your ingredients.



Allen

 

Nori is about 30% protein and low in fat, so a good rule of thumb might be that you could double the amount of nori you are feeding on a DMB compared to the DMB of whole animal feeds. (because they have twice the protein and fat) Nori (Porphyra sp.) is low in phosphorous, (follow link to Nori/Laver analysis) .....about .5% so this is also about half of what you would expect in whole animals.

So I would say 1 gram or Nori would put a similar load on the system than 1/2 gram of whole animals (DMB)

You would need to weigh out some sheets to tell people how many square inches insheets this is by volume.... but different sheets are different thicknesses, so again, everything should be weight based, not volume.

 

Ok, So you are making a frozen food out of this? Anything you make into a slurry is going to be close to 85% moisture if not more (I see you are adding quite a few liquid products) so you shouldn't be far off of any other frozen food when you are done.

Yes, you could use this method to compare input and output of the system.. but the growth of the animals/corals in your system is also going to be removing nutrients from the water column. Fish use nitrogen to grow and phosphorous to make bone for example. Your true measure of efficiency would have to be in a system where you are only adding food and letting bacteria do the rest.... but this wouldn't really have much more value than just checking your nitrate and phosphate levels in the water.