Protein Skimmate and Copepod Production

By Diane Bennett

Concept

At the request of an org member I did a small experiment to find out if the "sludge" removed from a protein skimmer's cup (herein refered to as "skimmate") has any affect on the growth of copepods.

I have been asked to write a small article about my results. I'd like to preface this article with the admission that I am NOT a scientist. I took care to be consistent, but I used absolutely no scientific instruments to determine any quantity of copepods.

The set-up:

Under two 40 watt shop light bulbs I set up 5 clear plastic one gallon jars. I filled them with one gallon each of water siphoned off the glass of an aquarium known to have a thriving population of copepods by evidence on the glass. Water parameters of the original sample were SG – 1.024 ammonia 0 nitrites 0 nitrates <10ppm PH 8.2. At no time were parameters tested again in any jar. Each jar received a predetermined amount of skimmate at predetermined intervals as described below:

  • T1: Control tank 
  • T2: 1ml of skimmate every 4 days 
  • T3: 20ml of skimmate every 4 days 
  • T4: 50ml of skimmate every 4 days T

  • 5: 10ml of skimmate DAILY........ 

All skimmate was a homogenous mixture originating from the same source jar of collected skimmate, so the "quality" of the skimmate was consistent for all jars. Lights were on 11 hours daily. I began the experiment on 4/18 and the dosing schedule was as follows:

  • T1: no skimmate dosage at any time 
  • T2: dosed on 4/18, 4/22, 4/26, 5/1,5/5, 5/10, 5/14, 5/18, 5/22 
  • T3: dosed on 4/18, 4/22, 4/26, 5/1,5/5, 5/10, 5/14, 5/18, 5/22 
  • T4: dosed on 4/18, 4/22, 4/26, 5/1,5/5, 5/10, 5/14, 5/18, 5/22 
  • T5: dosed on 4/18, 4/19, 4/20, 4/21, 4/22, 4/24, 4/25, 4/27, 4/28, 4/29, 4/30, 5/1, 5/3, 5/4, 5/5, 5/6, 5/7, 5/8, 5/10, 5/11, 5/13, 5/14, 5/15, 5/16, 5/17, 5/18, 5/19, 5/20, 5/21, 5/22 

By the end of April there were noticeable pods in all jars.

Ok, Now the hard part: Measuring how many copepods each jar had in comparison to the others. The test itself isn't very scientifically controlled, but I really tried to rack my brain to figure out a way to make it a little more objective, and not just "I think this one has more". Because see, when you look at your aquarium glass, there are some areas with tons of pods and some with not so many and the jars were like that too. So here's what I did. On each jar, I marked 3 one inch squares - one near the surface, one midlevel, and one at the bottom of the jar. Then every four days I tried my best to count the pods (my eyesight may never recover!) in the squares and add them together for a total of that particular jar. I'm including the numbers here, but like I said, it's really just a guide to be able to make a guess.

After the first week, I decided to "feed" the pods and so added just a couple of flakes of food once a week.

Here are the results:

 

T1

T2

T3

T4

T5

1 May

5

8

9

9

12

5 May

7

13

15

8

19

10 May

8

11

12

15

12

14 May

10

13

23

11

25

18 May

11

20

15

12

25

These numbers might not seem like a whole lot of copepods, but remember, I was only counting on three very small areas, and only the copepods I could see with my own eyes! So what does it all mean? At best the results are interesting. It would appear that the presence of skimmate does help the culture of copepods, but there does seem to be a point of diminishing returns. At no time did any of the jars look to be "teeming" with copepods. I wouldn't recommend this as a method for culturing copepods, only because of the volume necessary to culture any useable quantity for something like SH fry. I think that it would be helpful for someone to duplicate this experiment to see if the results would be similar, or even to see if the results would be different with much higher concentrations of skimmate.

As for the population of copepods in our aquariums, it seems to be indicated that "over-skimming" could adversely effect the growth of copepods in our systems, but clearly more studies are needed.


Last updated by testperson on 2005-11-22

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