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Re:Paul's high-low light tanks

> Crypts are tolerant of a wide range of light levels, and it is easier to
> keep them in relatively low light because nutrients aren't drawn down so
> rapidly, and there is less chance of algae take-overs.  They can be grown
> in high light, and they do very well, provided that you keep the nutrients
> up and the algae under control.  I have sometimes had very good growth with
> Crypts in tanks that got sun.  I have also had good growth sometimes in 15
> gallon tanks with four 17 or 18 watt T-8 bulbs, although I have also had
> algae take-overs that my snails and Daphnia never seemed to be able to
> control.

In my experience, snails- Daphnia seem to be able to deal with about 3
(maybe more) watts a gallon on such a tank. Shrimps seems to be the answer
for most of the higher lit tanks for me.
> I have just started working with the compact fluorescents, and the problem
> of algae take-overs seems much greater.


 With these powerful lights (80
> watts on a 15 gallon tank) I have had a tank go very low in nutrients, even
> when I thought I was adding enough.

This sure is fun watching them levels go down fast though:)

  Since the plants looked extremely
> nitrogen deficient, I added a larger dose, and green water took over in one
> day.  In just one day, the tank went from clear to a dense green that I
> couldn't see more than three inches into.

I found adding 1/4 to less doses of KNO3 than I thought would be needed( say
2ppm compared to 5-10ppm of NO3) and trying to make up the difference with
shrimps/fish and extra feedings solved that problem for me.
Another solution that I tried was adding a small trickle plant filter off
the back with a peace lily in it.
It is a good nutrient sump when the N gets to high if you happen to add too
much. Also adds some CO2 stability if yours goes sour since the peace lily
is out of water, it doesn't need any CO2, just nutrients.

 Also, all the mulm at the bottom
> develped bubbles, and about half of it rose to the surface and turned into
> a cyanobacteria mat.   I currently am entertaining a hypothesis that my
> algae-control crew, snails and Daphnia, do not do well on algae that is
> highly nitrogen deficient, and the algae can accumulate, although it isn't
> especially visible.  Under these conditions, the plants look severely
> deficient, too.  When I add a big dose of nutrients, the algae takes over
> in only a day or two in the intense light, and the nutrients and CO2 get
> sucked down to zero rapidly.  the snails and Daphnia don't have a chance.
> With the very intense light, the green water actually killed the Daphnia
> population, which under dimmer light would thrive on and eliminate the
> green water.
Snails do produce a fair amount of mulm/waste but I wonder if it is enough
to satisfy a high light tank without running the risk of Algae. Shrimps seem
to produce lots of waste as well. In high numbers they seem to out eat many
animals and produce lots of waste which may or may not translate into NH4+
and a little NO3.
I have induced GW on purpose 3 times so far and dealt with it on several
other occasions by doing the same thing as Paul mentioned. I add to many
Jobes into the gravel or not deep enough etc or the tank was new etc.
On purpose I added jobes directly to the column. These were 15-15-15's in
each case. I added 4 to each tank(20 gallon).

I have a set up to remove GW fast as it appears so I can get back to square
one fast and do another run without having a messy tank. I use a HOT magnum
with a micron and an 8 watt Aquanetics UV in line and that takes fast care
of any GW. If I let it run for 2-3 days the GW will not come back. I
typically will do a water change before I add this to the tank and let run
after. I do add Trace elements and K2SO4 and food but no KNO3 or extremely
small amounts (1-2ppm if that).

Because it is very easy to get rid of, does not do much if any real damage
to a planted tank, I find it a good study to control.
> I want to see what happens if I start a tank with lower light, get the
> nutrients high and the snails and Daphnia on top of things, and then switch
> to the compact fluorescents and keep the nutrients high by testing daily
> and adding hefty doses.  Since I suspect that the algae gets all set for a
> take-over when the nutrients are low, making the algae possibly inedible
> or, at least, non-nutritious, for snails and Daphnia, I am hoping that by
> keeping the nutrients high, the algae will remain nutritious and edible,
> and the snails and Daphnia will be able to keep it under control.  We will
> see.

Nutritious algae......hummm? I like this notion.

> I have a low light tank (about 1 watt per gallon from a T-12 lightstick
> with a piece of aluminum foil serving as a poor reflector) with some crypts
> that look quite nice, although they have grown very slowly.  the tank also
> has a big bunch of Microsorum and floating Ceratopteris, further shading
> the Crypts.  This is a guppy tank, with no Daphnia, obviously.  I havn't
> taken a nitrate reading for a long time, but I would be surprised if the
> nitrates were not at least 10 ppm nitrate-N.  I would like to see what
> happens to this nice stable system when I pop the 80 watts of compact
> fluorescent on it.  My guess is, that the nitrates would drop rapidly, and
> so would the CO2, provided that I did not start supplementing what the
> guppies normally add.  The pH would go up to over 8, the nitrates down to
> zero, and green water would take over.

So is it the CO2 or the NO3? I would say the NO3 myself since I kept up the
CO2 to high levels throughout the runs I did.
I would further say that keeping the NO3 lower than typically suggested has
done a number on algae like Green spot and the others. But how does one keep
the NO3 low(er) without going too far and getting deficiencies?
Extra food did it for myself and  smaller amounts of KNO3.
This keeps the Phosphate up as well (from the food-flake in my case) but in
low amounts while giving some N from the preferred NH4+ form. This method
doses daily small amounts of food which get turned into plant
This allows me not to worry if I added too much NO3 etc. resulting in a
crashed tank.

Another method to solve this issue can be to use the substrate that is
loaded to some degree, but it by itself on a high light tank won't solve the
problems. It can solve perhaps 1/2?
It can be of great service on a lower light tank in the 1-2watts range

I've watched my phosphate drop fast in high light tanks like the NO3 but
perhaps at 1/10 the speed/ratio. Depends on the day tested:) How starved the
plants were prior to additions etc.
Real hard to say but for myself.
FWIW regards, 
Tom Barr
> Paul Krombholz, in cool, dry, central Mississippi.