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Re: Sand filters



 I have used several different brands of sand filter. They are great at handling heavy loads of fish or for tanks where the bioload is constantly changing, like grow out tanks or holding tanks. Because the sand grains jostle against each other, the grains gradually get smaller and you have to keep throttling back the flow or sand will begin shooting out into the aquarium. When it does, it will eventually find its way back in to the filter through the impeller which will, big surprise, look like it's been sandblasted. You do have to watch, tweak, and periodically replace the sand with new full-size sand once every few months or so. Some brands seem to chew up the sand faster or slower. We have had the eggs of tubeworms, several marine snails, and small creatures make it through the impeller and begin growing in the sand filter. The housing can get covered inside with calcareous algae. It's never gotten thick enough to interfere with function, but I suppose it could. Clogging has not been a problem I've encountered.  I have heard of the sand clogging with algae in freshwater or saltwater use, but keeping the unit shielded from light should prevent that.
  
----- Original Message -----
From: Erik Pfingstner
Sent: Monday, July 22, 2002 5:55 PM
To: killietalk at aka_org
Subject: AW: AW: nitrate filter
  
Hi again Tyrone,

I understand the first part, not later:


> My friend has a 22 litre drum which gets fed a small portion of the
> return water from his sump/filter. This tum is so effective that it
> dropped the NO3- levels from about 40 mg/ml to about 20 after one
> week of operation. It is still going strong and keep the NO3- levels
> in his ~3'500 L malawi cichlid grow out system composed of 7 ~500 L
> tubs.

So far everything is clear.

>
> He turns that system over 4x every hour and has crystal clear water
> all year round inspite of lots of sun shine---

What do you mean that he turns over his system 4 times every hour?


> There was an article in AFM a while back on designing the optimum
> anaerobic filter. I think the specs were a 2 meter 5 mm tube with a
> flow rate of 2 ml/min...

Do you mean a 5 mm tube without filter medium in it?

2 ml/ min that means 2,88 litters per day. That is 0.76 gals per day. If the
figures are correct, you cannot effectively remove nitrates without having
many of these 2 meters pipes of 5 mm width.

>
> In essence if you want reallly GREAT filtration switch to a sand
> filter. Run the outlet the "dark box" with course filter medium and
> then through shell grit to neutralize any nasty H+ ions that are left
> over. I personally prefer the planted tank concept.:-)


That is a good advice. Yet my filter also works perfectly to keep nitrates
at zero. This time, I will measure the effects on phosphates and let you
know. I will also post a description including drawing of the components
once I got my scanner to run.

Tell me, do sand filters do not tend to clog and let no water flow after  a
while? I dont know, I am just asking.

Erik




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