The
Miller In-Tank Denitrator
What are Nitrates?
Under normal conditions an aquarium, whether salt
or freshwater, builds up Nitrates. It is the final phase of the Nitrogen
Cycle. Fish waste and other decaying matter in the tank give off
Ammonia. The Ammonia is changed into Nitrites by the aerobic bacteria and
nitrosomonas in the live rock, aquarium surfaces and bio wheels.
Another group of bacteria called Nitrobacters transform the Nitrites into
Nitrates. Nitrates are basically fertilizers which would be used by plants
to complete the cycle. In the absence of plants Nitrates build up in the
tank and will become toxic to the inhabitants and will cause algae to grow more
quickly. Algae is a plant.
The only effective way to remove the Nitrates
from the tank is to do periodic water changes. Usually up to 25% at a
time. Commercial nitrate removers are available on the market that reduce
Nitrates by providing a surface for Nitrate eating anaerobic bacteria to form
changing Nitrates into Nitrogen gas. These bacteria can only do the job in
a low flow environment. The flow through this media should be in the range
of 1-2 gallons per hour and no faster. If the water moves too fast the
Nitrates are not converted.
The Miller In-Tank Denitrator:
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A low flow environment can be built using an
old under gravel filter riser tube. The outlet where the bubbles usually
come out must be blocked. Use a cork or rubber stopper. Place some
filter floss material at the bottom and fill with Seachem De-Nitrate or a
similar product. Place more filter floss at the top and put the cap
on. Run an air tube from the top of the riser tube to the air inlet
of a powerhead. The air inlet normally sucks in air to create
bubbles but underwater it sucks in more water. Perfect!
I just measured the flow rate and it came out to
7.5GPH. Too high! It needs to be around 2GPH. I will be
adding a air valve to the line to reduce the flow.
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Here you can see the finished De-Nitrator along with
some filter floss and SeaChem De-Nitrate. Click for a closeup. |
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Once placed in the tank and connected to the powerhead your
work is done. Click for a closeup.
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Does it work?
To put it bluntly: I don't know. In theory it should
work. Adjusted to 2 Gallons per hour it should cycle the whole tank almost every
12 hours. If I can find a reliable and easy-to-read nitrate tester I will
post some results.
Does this mean I don't have to change the water?
Even if it does work it is not likely to replace scheduled water
changes. It can only supplement Nitrogen removal and surely can't hurt.
We'll see once the bacteria starts forming and doing it's job. I'll post
the results. Bookmark this page and check back later.
5-17-01
2 Months later - Nitrates level at 5ppm. (kind of high) I hate my nitrate
tester. It's hard to read. I've been abusing my water changing
schedule to see if the denitrator works. I think the flow is too slow. A
partly blocked powerhead intake could have had an effect. I cleaned the
powerhead and increased the flow by adjusting the airline valve. More
results soon...
