[Coral-List] Use of Germanium Oxide to Control Diatom Growth

Julian Sprung julian at twolittlefishies.com
Mon Apr 25 10:02:31 EDT 2005

Dear Bethan,

You are culturing TWO creatures that aquarists have learned to control, though not universally. 

Diatoms are easy to manage by using reverse osmosis water to mix the artificial seawater and for top off of evaporation. (thus limiting the supply of silicate). It is normal to have them grow even at limited silicate concentration when you (the aquarist) constantly siphon and disturb the substrata. You should have a (calcareous- aragonite) sandbed in the system and let it develop a population of bacteria, protozoans, worms, copepods, amphipods etc. which will become a stable comunity that grazes on the diatoms that grow. Thus you won't notice diatoms on the substrata. 

For the viewing windows, it helps to employ some herbivorous snails, such as Astraea, Turbo, or Trochus. These should be easy to find in the UK at a pet shop carrying marinelife. You can get a handful of "live sand" from a pet shop to get the abovementioned life for the sandbed.

If your set up must be without sand, then you could employ just the snails to control the diatoms on all surfaces.

In addition, maintaining an alkalinity level at or slightly above natural seawater values seems to curb the growth of diatoms on the viewing windows. This can be managed with the use of "kalkwasser," a saturated solution of calcium hydroxide. It can be added by a dosing system for top off, or manually at a rate of 0.8g (1/4 teaspoon) dry calcium hydroxide mixed in 1/2 liter of freshwater added per 50 gallons of aquarium volume. This must be added to a strong current to mix it well in the aquarium. Aiptasia don't like "kalkwasser" being poured on them.

Nevermind the germanium route-


Julian Sprung.

> ----------
> From: 	coral-list-bounces at coral.aoml.noaa.gov on behalf of B.Thompson
> Sent: 	Saturday, April 23, 2005 7:45 AM
> To: 	coral-list at coral.aoml.noaa.gov
> Subject: 	[Coral-List] Use of Germanium Oxide to Control Diatom Growth
> Hi,
> I am doing some research using the tropical anemone Aiptasia
> sp. and am having some problems with diatom growth in my aquaria.  I am
> aware that adding very small quantities of Germanium Dioxide (0.0005g/l)
> to the water can inhibit diatom growth, however I'm concerned that it
> may also affect the populations of zooxanthellae.
> I would be grateful to hear from anybody who has experience of
> using Germanium Dioxide for this purpose, or who can suggest another
> method for reducing diatom growth.
> Thanks,
> Bethan.
> -- 
> B.Thompson         osp02a at bangor.ac.uk
> PhD Candidate
> School of Ocean Sciences
> University of Wales, Bangor
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