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RE: Tank conversion

Henry Hatch is querying the easiest way to convert his 75 gal. fish only
tank to a laterite based plant tank. Your plan sounds workable Henry, but it
sounds like you plan to keep the fish in the tank during the conversion and
to keep the tank running as you add more gravel, balls of laterite (Duplarit
K I presume), and then plant the tank. I don't think I'd want to be your
fish. The disturbance which would be caused by your method would be certain
to stress them out big time.

A tank that has been set up for only two months is still quite young - the
biological cycles that take place within it are only beginning to settle
down by this point, provided that your "moderate" fish load is not being
overfed and you have adequate filtration. You state that you intend to
reduce the fish load temporarily - do you have the space to remove the fish
altogether, at least for a few days? Can your filter (I'm hoping that it is
an external power filter or canister filter) be removed but yet kept in
operation (i.e. placed on another tank while you work on the 75 gal. one.)?

You also mention that your nitrates are 13 ppm - is this Nitrate-N or

(check your test kit instructions - it should say whether it reads NO3-N or
NO3. You convert NO3-N readings to actual NO3 by multiplying by 4.4)

If your Nitrate test kit reads NO3-N (most do, I believe), then your actual
Nitrate level is 57 ppm NO3. This level of NO3 is quite typical of a fish
only tank with a lot of well fed fish but much too high for a plant tank. If
you have been monitoring the NH3 and NO2 levels and you've noticed that
recently both of those have fallen to nil or very close to it and your
Nitrate level has only recently risen to it's current level, that's an
indication of a cycled biological filter, something that would be expected
at around the two month mark of a new tank.

What are the nitrate readings and phosphate readings on your tap water? You
ARE doing regular water changes now I hope? What is the frequency and volume
of your water change schedule? If your tap water has a lower Nitrate and
Phosphate reading than your aquarium, the excess is coming from your fish
food and its processing by your fish and filter system.

How clean is your current substrate? Does it contain much mulm (fish poop)?
Covering this with another half inch of new gravel may or may not cause a
problem, depending upon it's quantity and state of mineralization. A lot
depends on the size and number of fish you have, and how much they are being

Your expected light level (approximately 3 W per gal) will be fine for your
plants and your plan to plant heavily with fast growing plants is also a
good one. At this light level, additional CO2 will be very beneficial to
plant growth. Reducing the fish load is wise, but if you have an
functioning, conditioned, external filter, reducing the fish load will do
more for allowing your new plants to take root and not be disturbed by the
fish than it will to wreck havoc with the condition of the tank.

If it were MY tank, and I had a spare tank or any other container which
could hold the fish AND the filter for a few days to a week, I'd relocate
the fish AND the filter, then break down the 75 gal. tank, rinse the gravel
(just run it under 75 degree tap water for a few seconds, long enough to get
rid of any mulm), and then do the "Dupla shuffle" - 1/3 of the gravel (in
your case, 1") mixed with the appropriate amount of Duplarit G (or other
granular laterite), and then top it with the other 2/3 (2") of clean, washed
gravel. Fill the tank to around 80% of capacity with new water, add your
favourite water conditioner and then place your plants. Once you have
planted the tank, you can top up the water level, install your lights and
CO2 and wait a few days for things to settle down (the tank will probably be
a little murky from the gravel, but a lot less so than if you followed your
original plan). The lack of a filter on the newly re-set tank won't matter
for a few days - but you could put in a power head temporarily to provide
water movement if you wish.

Once the tank has had a few days to settle in, I'd install the still
functioning external power or canister filter and introduce the fish (making
sure of course that the water conditions are similar in the holding tank and
the aquarium). Your 75 gallon tank will now have a functioning biological
filter (hopefully you are not running an undergravel filter now - if you
are, all bets are off and none of this matters), you have a clean laterite
based substrate and a lot of new plants eager to grow and develop. You
should, if at all possible, keep out any fish which like to root around in
the gravel for the first couple of weeks, to give the plants a chance to set
root but things like characins or small tetras should be fine.

Hope this helps - and sorry to all of the old timers for the length of the
post, but this topic is more germain to the list than political discussions
over Vectrapoint, in my opinion anyway. ;-)

James Purchase
Toronto, Ontario
jpurch at interlog_com