So it sounds as if it really doesn't matter who's pump you use. Just as long
as it's a low head, low rpm pump that has alot of slop as far as tolerences
go between the impeller and the impeller housing. More room for the critters
to pass without actually coming into contact with any spinning parts. the
greater the odds of any particular plankton making it thru alive or at least
without too much damage. Also, by removing any burrs or uneven spots on the
impeller blades lessen the chance that the imperfection will create micro
sized areas of low pressure behind the imperfections trailing edge.
Cavitation is simply areas of pressure so low that water is no longer able
to remain a solid but instead boils itself back into it's gasious state. Any
plankton getting itself sucked into the area of low pressure and it's going
to find it's insides are boiled as well.
If you really want to minimize the amount of plankton being killed, nothing
beats a diaphram pump. I have two that I picked up at an surplus restrauant
supply busines for less then $20 bucks. One pumps about a quart per stroke
the other slightly more. Both are noticibly louder then a powerhead that is
in good working order. Maximum flowrates are around 250 gph. Perfect for
creating surge areas that are very similar to actual wave action. And
perfect for plankton because the only moving parts are the diaphram itself
and the two reed valves made of rubber.
Now... whether or not any of this is going to increase the growthrates of
the majority of corals that reside in our aquariums...Lets just say that I
keep an open mind.
"Richard Reynolds" wrote in message
news:adO8c.13197$_U.6261@lakeread05...
also some of the rio's are more plankton friendly than mag/maxijet

How do you know? I don't disbelieve you, it's just that this
(plankton mortality in pumps) is a subject of real interest to me
and I'd like to know what information you have.

its been published before, its not so easy to find but its out there on
the vast internet,
but basically certain things can go thru certain pumps at certain rates,
and id have to
search for the data.

some of the rio's fall into this, and in every category that *I* am
interested in a rio
180 fits for some thing it needs mods for others doesnt the 1100 is
another that fits into
some areas.

in every case when the pump is not made specifically to work with things
like phyto it
requires a careful exam and sanding down any imperfections from when the
plastic went thru
the mold or whatever they do it can leave lips or extra small pieces.
along with that no
pump is 100% plankton friendly you have to pick your planktons and
guage how much harm
is acceptiable, a note i did say "more plankton friendly"!

a starting place you can pump rotifers thru a rio 180, they will live,
they will drop
there eggs so you cant use it in the culture, but you can use it to move
the cultured
rotifers. it also means you can use it in a rearing tank (but you *must*
keep the fry out)
a parastolic pump is the same way if you set the rate up to high they will
drop there
eggs, the catch you can turn down a parastolic pump you cant really turn
down most
powerheads (closing a valve doesnt cut it) most of the smaller 30micron
zooplankton
things like cilliates are also safe going thru a rio 180

copepods are the same as rotifers if you have the pump within the culture
container you
will kill the culture, by removing the eggs but you can use them to pump
from the culture
into your tank

another angle most pumps will pump nano without harm, even inside the
culture container
but only a few will pump tetraselmise the cell wall is to thin, the cells
break down and
you begin to pump mush. however you can modify a rio to be able to pump
tetraselmise its
not hard some sanding here and there shorten the blades on the impeller
and away you go.
that same modified impeller will now also pump baby mysis.

id have to dig around to be certain of all the models. ive already
selected them, so I
know that the ones I picked were good, and past that I didnt need the
data.

--
Richard Reynolds