Reference for mortality of microplankton in powerheads

[Mike_Noren]

Does anyone have a reference for the percentage of various types of single-celled plankton killed during passage through powerheads/aquarium-type filters?

I'm pretty sure I've seen an article like that posted here on reefcentral, but searching turns up nothing.

 

[dave willmore]

Nobody else has answered so I'll venture out on a limb. I don't know of any scientific references and would like to see them also. I have read that copepods are the largest animal biomass on earth, and i think we should keep them in our tanks and culture them as coral food. I know a lot of people will disagree with my opinion here, but my readings indicate that the long fragile antennae of calanoid Copepods almost never survive intact after passing through a 1750 rpm impeller pump and pumps cause extremely high copepod mortality. I think the assertion of pump makers and many noted authors of low damage to plankton by pumps is extremely off base.

While there are some microplankton with thick cell walls and no cilia or flagellates, they are the exception to the rule. Nearly all plankton have locomotion devices, cilia, tails or flagella that probably gets damaged by pumps.

It doesnt have to be physically contacted or sheared by the impeller edge, the "zero to sixty" acceleration should be enough to rip off the cilia all by itself. The G force of massive acceleration is something that micro plankton have never evolved to survive and my understanding is that practically no plankter will pass through in one piece, especially when they go through the pump 10 times per hour (240 times per day). Even if a "plankton friendly" pump causes 1 percent mortality, this would be 10 percent per hour.

It is true that you will always see little animals on the glass near the bottom of the tank, but these are benthic animals and are typically planktonic for just a portion of their lives. It is also true that some animals will survive the acceleration of the pump but I think they are a small minority.

I say this without a lot of scientific data and will probably draw the ire many water pump advocates, but as i used to say as a kid "thats my story and I'm sticking to it"!

 

[dave willmore]

Sorry about the double post. I'm still trying to get used to the new iPad.

 

[t.trezona]

Adult copepods will be chopped up. Their eggs however are not. These (the eggs) are the food your corals are capturing. There are a number of references in RC to this.

 

[dave willmore]

Tom, thanks for this information. It makes sense that eggs and cysts could survive the process. To ensure that both eggsa and adults live a complete natural life (until being eaten by corals!) I move water with a large, slow turning propeller. It uses the same amount of elecricity and moves the same amount of water, but without the damage. I understand that large props would be very unsightly on small tanks, but so far I haven't found a method that moves water safely and also comes in a small neat package.

 

[Mike_Noren]

I doubt any large planktonic organism (such as copepods or fish larvae) have any chance to survive in a reef type setup where the water passes through a powerhead several times per hour. The pressure gradients inside the pumps kill them.

I'm specifically wondering about single-celled organisms. Obviously some can survive passage through powerheads (as proven by the fact that one can get "green water"), but my sampling in aquaria suggests that survival is poor, and uneven between groups. Both density and diversity are very low - I pretty much only found a few very small ciliates, green flagellates and the occasional pennate diatom.

I know that I have read a paper on plankton survival in impeller pumps, and I think it was posted here on Reefcentral some 4-5 years ago, and was hoping someone would remember.

 

[doctorgori]

...we just setup a FOWL tank and somehow the lil beasties from the chaeto in the sump made it up to the tank via the pump....
whether this was as adults or eggs or whatever, I dunno...but I seriously doubt a pump impeller acts as a efficient barrier for bugs and plankton and such

 

[Mike_Noren]

I seriously doubt a pump impeller acts as a efficient barrier for bugs and plankton and such

It's clearly efficient at killing off those animals which pass through it ten times or more per hour - the planktonic ones which live in the water. Maybe the filter kills only, say, ten percent each pass, but that still means planktonic organisms which have to pass it maybe 1500 times to complete their life cycle are toast.
That's why there's plenty of harpacticoid copepods (the kind which lives on surfaces and only rarely go swimming) in reef tanks, but no calanoid and very few copepodid copepods (which spend most or all of their lives swimming).

 

[Luis A M]

IMO the killing capacity of centrifugal pumps has been grossly overestimated since Addeys book.
It is easy to see how bbs pass unharmed thru them.
But I dont see the point here since phyto and zooplankton wont survive in a typical reef tank,no matter the type of pumps used.

 

[dave willmore]

Luis, are you saying that survival doesn't occur because of the skimmer, polyp predation, or some other factor?

 

[Luis A M]

I cant say for sure,but plankton dissapears soon of reef and fish tanks.Tank wall diatoms and harp.copepods are not part of plankton.

 

[t.trezona]

I had a previous system where I grew Copepods and Amphipods in a separate tank. The tank fed directly to a Sequence 5900 pump which fed my display tank. The display was teething with the critters all the time, despite having a load of fish. The adults may have been chopped up by the pump but the eggs/cyst certainly were not. Never added any directly to the display.They had to have come from somewhere. As I said previously there are a number of references in RC to support this.

 

[dave willmore]

Was the display teeming with critters in the substrate and attached to the glass, or was it snowing fine specks in the water column? I am sure that many things survive the impeller pumps, but I'm also sure that ciliated and flagellated algae cells and copepod antennae have a hard time. Like yours, my system also has separate refugiums for calanoid copepods, rotifers and artemia, but I'm considering using things like the Tom's aqualifter to pump concentrated zooplankton up to feed the display tank.

 

[doctorgori]

...all I know is whatever lil critters you put in the sump somehow ends up in the display tank....
...maybe if they pass through the pump a few times it kills them, I can't argue either way, but I wouldn't use a sump for a quarantine tank, or to isolate parasitic isopods, thats for sure

 

[t.trezona]

Whatever you put in your sump will definitely wind up in your display.

 

[dave willmore]

I think we are talking about two different subjects. Both points are correct. Mike's question regarded single celled plankton survival of impeller pumps, and my answer was that pelagic plankton have evolved locomotive and prey finding appendages with poor survival from the acceleration forces of impeller pumps.

It has also been correctly pointed out that many small and large organisms in fact do survive pumps -- benthic organisms, parasitic cysts, eggs of some calanoid copepods, hard shelled crustaceans and probably many others. Thanks for pointing this out.

I think we all agree that pelagic organisms become excluded from reef tanks. Studies show organisms with locomotive cillia, flagellae or fine antennae are severely injured by impeller pumps. Mike wants to see the research.

Perhaps Mike's question cannot be definitively answered. Perhaps nobody can say for sure what percentage of plankton exclusion is caused by impeller pumps, polyp predation or skimmer removal. But I think we all intuitively understand that some combination of these three plankton killers is removing most of the pelagic plankton from reef tanks.

Does this sound right?