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[APD] Blackening Java fern
I've seen and cured this several times.
I went back and reduced the CO2 on purpose to see (a little) and
got the same response.
This is at 82F, KH of 5, Gh of 7.
The tank had a peroid of good growth and as biomass of the
plants increased dramatically, a few species started acting
As you increase the PLANT biomass of a tank, is it safe to
assume that you also increase the CO2 uptake/demand for this
biomass you now have a lot more of??(Idea!).
Now this amount is fine when you have less plant biomass right?
That's a safe assumption.
Some plants are wimpy when it comes to getting their fair share
of nutrients/CO2 than others. Folks carry on and on about algae
plant competiting all the while missing the big picture with
competition: plant plant competition.
Amano and others have speculated allelopathy is the cause.
I've speculated and falsified every test I've done with that.
Does not mean it might not occur but not in any system I've ever
seen and there's not once bit of research to suggest in natural
systems to date either.
There is on the other hand........a great deal of evidence that
plant- plant competition for nutrients and especially CO2 does
occur in nature and in our own tanks........
But.......many aquarist don't see it.
Every bit of evidence to date suggest Java ferns can only use
CO2, not bicarbonate. Same with Bolbitus.
So when the other weedy faster growing plants are gobbling up
the last bit of crannberry sauce, I mean CO2, the java fern does
not. It turns black fairly quick, Bolbitus is even faster.
If you remove the competitors and/or reduce the lighting and/or
add more CO2, the plants do grow back(they grow slow so you need
to wait for them to respond, most folks don't!!)
Rather than just observing, I tested my idea: I added slightly
less CO2, and the ferns blackened up good, took about week and
takes about 3-4 weeks for them to regrow good.
Next I tried maintain more CO2 to match the plant biomass. As
you have more plant biomass, the amount of mixing in the water
is reduced also, so you need more current as well to get the
same amount of CO2. To address this, I paced the plants in the
path of the CO2 outlet and allowed the other weeds to grow out
The tank have 60-80% weekly water changes, not much chemical -
chemical issues, this has never been shown in the research, but
if I added activated carbon to the filter, that would also be
addressed fully, but I did not do that. If some one wants to
argue it's a factor, they are welcomed to do such a test
themself! Don't argue without doing someting.
I've had client tanks that had the same types of things occur,
under high light/other competitors etc Java fern can be
outcompeted for CO2 and suffer.
I'd say other slow growers likely are in a similar situation.
At the same time this occured with the Java fern, the
Myriophyllum grew at a fast rate.
Note this is slightly sub BBA inducement range and it's hard to
say what the tank's CO2 demand really is tank to tank, time to
time due to such issues with changes of biomass through time,
flow characters, lighting, and other individual tank
This is more common in higher temp higher light tanks.
Now........why might that be?
Faster growth due to higher temps(nearly 2x at these temp ranges
we keep, thus 2x as much CO2 used as Carbon assimilation is a
good measure of growth)and faster growth from the high
light(again, maxing out the PS rates).
Take home measure: add more CO2 if you see smaller growing tips,
blackened java, if you can: reduce the temps(I don't), poor
general growth when the nutrients are good, use less light
folks!!, keep your tank well pruned and try to maintain Plant
Biomass stability, not just "nutrient stability", what doi think
happenes when you have 2x the biomass to the nutrient stability?
You assume things are stable and then you run out and then I
have folks claiming they had plenty of NO3 and now they have BGA
and stunted tips:)
Do tanks with less light have more stable conditions?
Yes, they do.
Gobble gobble the nutrients and the wetland plant, that
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