Vacuum cleaner

OK folks this may be a silly question but is there
such a thing, that will "hoover" the gravel but pump
back any water taken ?

Whenever I change the water (40% every two
days for this initial month), water seems to get quite
cloudy at first with the detritus from the gravel, this
cloudyness is dealt with by the filter and any "bits"
falling to the bottom fairly quickly, but what I would
like to do is apply a gentle vacuum to the gravel
(don't want to wash the gravel as this will remove
any "biolife"[is this the right name for the bacteria that
deal with the fish waste and turn nitrites into nitrates])
however I don't want it to suck out all the water so a
filter and pump the water back in might be the best
way to go. Forgive me if they (aquarium vacuums)
all.do this, and this is a bit of a non question.

Two comets in 5 gal (yes I know this is far too small)
With a gravel bottom (Goldfish with gravel).
--
yours S

Nihil curo de ista tua stulta superstitione

Go here to read more about cycling a fish tank. BTW, a five gallon
tank is too small for many types of fish but especially goldfish. Its
not even big enough for one of them. Please consider getting a larger
tank ASAP as I dont think your fish will live very long in the size
tank they are currently living in : (

I would not even bother trying to cycle this tank with two goldfish in
there its about impossible. I would do 100% water changes every day
until a larger tank or even rubber maid container is set up (they make
very nice temporary tanks with out the cost of an aquarium)

Oooppps! I forgot to provide the link to cycling a fish tank safely:
http://www.aquamaniacs.net/cyclingsafelyfishless.html