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Re: Gobs of stuff

Aquatect2 wrote about a tank that is consuming mass quantities of 
nitrate - as much as 6 ppm a day in a 60 gallon tank -  apparently 
because it was built with a plenum.

I ran a few numbers and scratched my chin a bit; I contemplated mechanisms
and controlling rates and recalled my own experience with denitrifying
setups.  This is certainly a lot more denitrification than I've heard
claimed by anyone else.  I think if it were all converted into nitrogen
gas (the normal route) the tank would generate more than 200cc of 
gas per day.  Someone else could check that if they like.  I assumed 
there was 50 gallons of water in the tank.

I don't suppose that's impossible, but is it likely?  I'd look for some 
other reason for the apparent high consumption of nitrate.


Adding NO3:  Frank Reiter wrote in re Karen Randall's cautions

> > I think you should be _very_ sure that your plants actually need more
> > nitrogen before trying this, and you should fell quite confident in your
> > ability to handle transient algae problems if you guess wrong.  If your
> > tank is less than 6 months old, and/or you are a novice aquatic
> > gardener, I
> > would be _very__VERY_ cautious about adding nitrate to your tank.
> I was quite surprised to read this strongly worded caution.  I add NO3 to my
> tank quite regularly, otherwise they fall quickly to 0 ppm.  When my levels
> drop below 10 ppm I dose enough to raise them again to 15 ppm.  Once,
> miscalculating the dosage, I got them to 30 ppm.  None of that has ever
> caused a problem for me.

I was not surprised at the strong wording, and might tend to state things
more strongly.  The reason is (as Karen alluded to) if nitrate is the
growth-limiting nutrient in your tank then adding nitrate will cause a
boom in growth - unfortunately that usually means a boom in algae growth. 
That is the functional definition of a limiting nutrient.  If you add
nitrate and growth doesn't increase, then nitrate wasn't growth limiting. 

The increased rate of growth continues until some other nutrient becomes
growth-limiting.  After the other nutrient becomes growth limiting
continued additions or increased additions of nitrate have little or no 
effect.  Thereafter, the growth rate remains elevated until the supply of 
the limiting nutrient is depleted.

That description assumes that nutrients rather than light levels are 
growth limiting.
> Before I started dosing NO3 I had terrible algae problems, and I have heard
> from others on this list that nitrate limited tanks encourage certain forms
> of algae.
> If your test kit shows 0 ppm, why would you wait for your plants to show
> damage before adding NO3?

Why would you add something if your plants don't have a need for it?  
Overdoing things almost always has some repercussion.

I've never dosed with nitrate, I have no regular algae problems and when I
do see one developing I can usually trace its cause to something simple -
usually to a change in lighting. 

I have three different nitrate test kits and usually get three different
results when I use them on my tanks.  Two of them give me their lowest
reading on the scale (different scales), and the third doesn't react at
all.  I interpret that to mean that I don't have much nitrate in my 
water.  Just the same, I don't have nitrate deficiency problems.  So what 

When we use nitrate tests to estimate the nitrogen supply in our tanks
then we neglect other sources of nitrogen.  For instance, I have malaysian
trumpet snails in my tanks.  They and other fauna in the substrate produce
waste ammonia, which is available directly to the plant roots.  I will
probably never measure that part of my tanks' nitrogen supply but it
very well may be a large part of my plant's nitrogen requirements. 


Now my own questions...


I picked up some Hydrocotyle leucocephala (pennywort) today.  I stuck it
into my nursery tank, planted as a usual stem plant with one end of the
stems inserted in the gravel.  I've also read of it being used as a ground
cover, with the stem planted horizontally.  It seems like it could make a
nice foreground plant that way, but I wonder about it's climbing out of
the substrate.  Have people had much success growing it that way? 


I took my kids down to the river today to do some wading about and while
they were about that I hunted for interesting things growing in the water. 
I found something odd and wondered if someone might recognize it from a

It was a soft - nearly gelatinous - translucent, chlorophyll-green blob
about an inch across.  One side was lumpy and wrinkled like a brain.  The
other side was concave and appeared to have been previously attached to
something.  My kids were wading around just upstream from where I found it
floating and I speculate that they dislodged it. 

My first reaction was that it was some type of algae, and my second that
it may have been some simple critter with an algal symbiont, or maybe
something like a freshwater sponge with algae growing in or on it. 

At any rate, I brought it home and placed it in a brightly lit, unfiltered 
tank, tied down to a stone with a length of fine monofilament.  Any idea 
what the thing might really be, and if so, then how I might better keep it?


I've long been interested in keeping filter-feeding critters in otherwise
unfiltered planted tanks.  I noticed that Arizona Aquatic Gardens sells
mussels.  I assume these are freshwater mussels, or at least that they
don't really care.  I have a tank where I've been successful keeping clams
but I remember someone on this list (Mark Fisher, possibly?) commenting
that mussels really can't be kept in an aquarium.

Any additional opinions, success stories or failures?  The tank I have in
mind is sunlit, heavily planted and unfiltered, with guppies, American Flag
fish, otos and shrimp.  Do the mussels need to be attached to something? 
Could they exist in the same tank with the clam? 

Roger Miller

In Albuquerque, enjoying a warm and dry early autumn.