Re: Aponogetons & growth cycles

Tom wrote:
> Do people recommend a really thorough deep vacuuming of the gravel, i.e. deep
> enough to disturb the laterite? Is this recommended only if algae problems 
> get bad?  Does the fish waste get broken down effectively in the gravel? 

I definitely wouldn't advise much vacuuming of the gravel, especially with
laterite. Why waste laterite and cloud the water? If there is so much fish
poop that it begins to cause nitrate and phosphate levels to get too high,
you should either reduce the amount of fish or do some "light" vacuuming that
doesn't disturb the gravel, roots, plants and laterite or other substrate
additives (like -ahem- vermiculite or earthworm casting soil ;-) No, just
because there is a bit of mulm on the gravel, you don't need to vacuum it
up. I also wouldn't mix conventional, high flow undergravel filters with
fine substrate additives. I'm sure someone else will have something to say
on this subject ;-)

> What controls plant growth cycles in an aquarium?  Specifically I'm wondering
> why without any change in water chnge routine, tank temp, or lighting 4 apono
> geton crispus plants lost all their leaves.  Do they have some built in 
> mechanism controlling the growth cycle (and therefore can't grow continuously)
> or were they responding to a subtle change in the tank.

You are touching on a subject near to my heart!  There are some strains or
hybrids of Aponogeton which grow fairly well in a CO2 environment with
sufficient light using plain gravel and some fertilization (biological or
bottled additive).  These plants won't do well in less than moderately optimal
conditions.  In the case of some Aponogetons (i.e.  madagascariensis lace
plant), my feeling is that we have to provide all the necessary conditions in
particular, the substrate.  The root system of these plants is extremely
important for long term viability.  You can't afford to be disturbing these
roots.  I have two lace plants which started from 2.5" bulbs that produced
spectacular growth for the first couple months.  I moved one to the 75 gal.
with the 250w MH and vermiculite/earthworm casting/gravel substrate as soon as I
was able to get it ready.  The one in the original tank shows almost no new
growth and most of the old leaves are now brown.  This may be due in part to a
lighting and CO2 failures while I was on vacation but even prior to that, the
growth differences were noticeable.  I also suspect that regular pruning of
older leaves may be necessary to encourage new growth.  I'm also suspicious of
my snails.  The one in the new tank took several weeks to re-establish itself
and is showing new leaf development but nowhere near the rate initially.  The
tank temperature is also high now (77-80) due to summer heating.  This has
pushed the plant into it's summer phase.  This winter I will try to let the
water temperature fall but it won't go below room temperature which
unfortunately doesn't get below 70 without serious complaints from my Filippine
wife.  In nature the plant has winter temperature of 50-60 at which time it
drops all leaves.  Spring time (clean water, more light, higher temp + ??)
causes the plant to begin the dramatic growth phase.  It has to have strong
roots, sufficient appropriate nutrients, algae free large leaves in order to
photosynthesize lots of starches into the tuber which are necessary to support
the growth phase.  I have heard of a fellow who gets continuous growth by
allowing his gold fish to munch on the leaves and provide a rich mulm for
fertilization.  I suspect that there is a way to fool the plant into continuous
growth just like we get African violets to flower and poinsettas to turn red by
controlling the duration of light.  In this case, the activators include light,
pH, water conditions in addition to the chemical biological clocks.  Maybe
trimming off adult leaves removes one of the chemical triggers?  I am using a
farlowella, 8 otocinclus and lots of snails to help keep algae off the leaves in
addition to the other things I mentioned.  Time will tell.  I may move the
second tuber soon too.

 - Steve