Copepod and Amphipod Density - How can one assess this?

[JavaJones]

My current set has been going for about 8 months now (although most of the LR has been with me for little over 3 years in other tanks that were consolidated into the current setup). I have noticed that microstars, bristleworms and asterinas seem to be flourishing. However, I have not noticed many copepods and amphipods in the tanks (either the 29 refugium or the main 75G display).

I have made a point of look for their activity a few hours after the lights are turned off but could not discern any. Similarly, my chaeto does seem to have much life in it (at least not the the naked eye). Is there any way for me to more definitively ascertain whether or not there's any problem here?

One thing I did a few months ago was drop an entire bottle's worth of tiger pods bought from Skipton's into the refugium. Is it possible that I created an imbalance of sorts?

Also, I have an abundance of tulip anemones, verging on a typicle majano infestation. Would these wipe out the pods?

I also have two mature engineer gobies that are constantly churning the sand in the display...could they engage in unsustainable harvesting of my pods? ;-)

I am really waiting for the day that I could add a mandarin fish without problems. I should add that I have had a yellow watchman for some months now and it seems to have no problems surviving in spite of getting little direct food from me...

 

[FishHead]

Copepod and Amphipod Density - How can one assess this?

oddly enough,,i recently came across an article in a 2001 issue of AFM describing the method to estimate amounts of various sandbed critters.
I'll dig it up later..

 

[~Flighty~]

Do you see any adults?

 

[NateHanson]

I also have two mature engineer gobies that are constantly churning the sand in the display...could they engage in unsustainable harvesting of my pods? ;-)

Bingo. I don't think "sand-sifting" critters are good for a small-medium reef tank. They strip the sandbed of life.

 

[JavaJones]

FishHead: Thanks for the article lead.

Flighty: I don't really see any adults (although mine are not the most discerning eyes).

Nate: Yes, that had been a nagging doubt for me... Still I cannot part with the gobies that have been with me since my SW tank cycled. Hopefully the 29G DSB Refugium becomes a reservoir...

 

[maurod]

I usually use the density of 'pods under my cleaning magnet of an indication of the density of the pods I cannot see.

 

[FishHead]

Found the info..not sure why you would bother with step 7 and just go right to step 8.

Live Sand Examination (Ron Shimek, AFM 2/00)

Materials
clear glass/plastic container
transparent stand to support bowl
intense light source
tweezers
hand lens(20xbest)
baster

Procedure
1) use a narrow felt-tip marker to make a rectangular grid on bottom of bowl. lines should be 1 centimeter apart.
2) Fill bowl with tank water and put on support. arrange the light source to illuminate from underneath(use mirror if necessary). keep light off.
3) take about 1 cubic centimeter of substrate from a selected site in tank
4) put sample in the container, stir to distribute evenly. s/b thin layer in container. too much will obscure organisms.
5) let sample sit for 5 min
6) turn on the light. examine using hand lens or microscope. look for movement.
thrashing: nematodes
coiling/slow movement: worms
rapid jerking: crustaceans
rapid gliding: flatworms or large ciliated protozoans
7) count and tabulate organisms
8) examine container closely by carefully clearing the sediment away from each grid square using tweezers.
9) count and tabulate organisms
10) total the numbers found
11) repeat several times to get an average of all values
12) multiply by 10,000 to find the number per square meter, the common scientific benthic measure.

Evaluation
0-1000 animals per sq meter
poor sand bed fauna

1000-5000
mediocre sand bed - rejuvinate and sample again in three months

5000-10,000
normal sand bed with low population numbers. feed system more heavily sample in three months.

10,000-100,000-plus
normal sand bed with natural range of numbers

 

[OceanGuy]

My kids take a depression slide with some tank water and a cover slip. They are never at a loss for life. Lots of naupillae, copepods, amphipods, tubeworms, etc.
and many, many small protists. You have only to look in a microscope to discover some really great life.