On 2003-11-20, Dave Millman wrote:
My 20Gal long tank, with 2wpg, had something happen to it a few
months ago. My plants stopped growing well.

IT sounds like you havea 20W bulb on there. Standard flourescent bulbs last
6-12 months before output drops significantly. This is the most obvious
thing to check.

It's a twin 20W flourescent bulb. Is this really the case? I've read
it around the groups plenty of times, but I never really believed it.
I'd put these bulbs at around two years old. I think I have some spares
- I'll swap them in and see how things go.

but I did the obvious things as the
plants slowly died off - stopped dosing fertilizer so much and cut down
the light.

Cutting down light is never a cure for anything, unless you have too much
light. Even if your bulb were new, this is not your problem. Turn it back
on 12 hours per day.

The symptom of too much nutrients is algae. You do not have that symptom,
so too much ferts is not the problem.

Well, I did when all my plants died and left the nutrients sitting in
the tank ::-) I cut down the light mostly to reduce work on myself when
I hadn't had a chance to replant everything.

As soon as the new plants went into the tank, I cranked it back up to 12
hours a day.

I change 3-4
gallons on a monthly basis. And this tank, exactly as I'm running it
now, was previously very, very successful.

This is a classic case: Originally your tap water had sufficient nutrients
for some plants, so they did well. Since you change so little water, you
replaced very little, and eventually something ran out (probably Potassium,
or if your tap water is soft, Calcium or Magnesium, although I don't know
what you dose.)

I'll give it a shot, sounds pretty reasonable. My water is very high
GH, medium-high kH.

My fertilizer regimen: I dose Kent Freshwater Plant Supplement (Iron,
Potash, Copper, Manganese, Molybdenum, Zinc) and Flourish Trace (some of
the above plus, Boron, Cobalt, Rubidium, Tin, Vanadium). I don't put in
as much as the bottle recommends since that's always tended to create
algae problems - I dose Kent twice a week, Flourish once.

Anyhow, thanks for the suggestions everyone!

--
Ross Vandegrift


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