|
|
|
Tank "Cycling"
To be honest, whenever I hear this term, I envisage
this large, all glass tank, riding around on a bicycle …..
The term "cycling" is actually a bit
of a misnomer, IMHO. In our hobby, it usually refers to a state where
the aerobic component of the filtration system has "matured"
to such an extent that there are enough aerobic bacteria present in the
system to convert the ammonia/um generated by the tank's bio-load into
nitrite, and the further conversion of the nitrite into nitrate. In actual
fact, this only completes of the first phase of the actual nitrogen cycle.
Until a few years ago, that was as far as the
process could go, resulting in a slowly increasing level of nitrate, which
could only be reduced by partial water changes. Thanks to the "discovery"
of live rock, and later of live sand, the "'cycle" can now be
completed by anoxic bacteria living in these substances, further converting
the nitrate into inert nitrogen gas.
In hobbyist’s terms, a new system is considered
to be "cycling" when there are still detectable levels of ammonia/um
and/or nitrite in the water. A system is considered to have "cycled"
when these levels drop to zero, and the nitrate level starts to increase.
The important thing to remember is that a tank
does not "cycle" only once. The system will reach equilibrium,
where there is enough aerobic bacteria living in the filters to maintain
an undetectable level of ammonia and nitrite with a given bio-load. Any
increase in the bio-load, such as when a new fish is added to the tank,
will upset this equilibrium, by "flooding" the system with more
ammonia/um than the bacteria can digest. Obviously, with more "food"
available for these bacteria, they will multiply (assuming that food was
the limiting factor), and in time the system will reach a new equilibrium,
able to handle this increased bio-load. This does take time, though, and
in the meantime the increased level of ammonia and/or nitrite could be
poisoning all the fish.
How to "Cycle" a new tank.
In order to "cycle" a new set-up, one
must introduce a source of ammonia/um. In the past, this was usually done
by adding some hardy fish (usually Damsels) to the new tank. Although
this works very well in a bare tank (with outside filtration), it’s
not recommended for two reasons:* It is cruel to keep any fish, no matter
how "hardy" in water containing near toxic levels of pollutants.
* Damsels are very aggressive, and once the tank
has "cycled", they consider the whole tank as their exclusive
territory. They will attack, and possibly kill, any new fish being introduced
to the tank. To make matters worse, the rock in a typical reef tank makes
it hard, if not totally impossible, to catch them when you eventually
decide to replace them.
I would start the cycling by initially
only adding the sand. Let it settle for 2-3 days, with all the circulation
going. Then, add one or two pieces of base quality live rock, and one
or two dead prawns or cocktail shrimps (the food type, not a dead one
from a LFS - that could be carrying any number of diseases!). At this
time, start testing the water for ammonia daily. You should notice an
increase in the reading, and after a few days, the reading should stabilise,
and then slowly start to drop (this could take 1-2 weeks). At that stage,
start testing for nitrite as well, and keep on testing for ammonia.
You should now notice an increase in nitrites, and a decrease of ammonia.
After another week or so, the ammonia level should be fairly low, and
the nitrite level should have reached it's peak.
Once the nitrite level has also started to drop, you can add the rest
of the base quality live rock, and once both the ammonia and nitrite levels
have become unreadable low, you can then add the good quality live rock
(containing many interesting inverts). This could cause another ammonia
& nitrite "spike", although it will be much smaller than
the first. This is not critical if you’re patient - just let the
tank settle for another month or two before adding fish. This should give
the macro algae and small critters on the LR time to recover, and to multiply
to sustainable levels in the LR, and to migrate into the sand. During
this time, you should also add some live sand, and/or some live sand "starter
kits" and "reef janitors". Also, don't be concerned with
the initial algae growths - it's quite normal to have some diatom, cyano,
and hair algae growing as the maturation progresses.
"Cycling" a new system with uncured live rock.
Introduce the LR after the tank's been up about
a week, and use it to cycle the tank. Wait at least two months before
introducing the first fish.
Advantages:
* You don't stress (or kill) any fish, and do
not have to add fish that you will have to remove at a later stage.
* You don't need to buy fully cured LR. In fact,
the cheaper, uncured LR causes a better cycle, and usually have more diverse
life forms in/on them.
* You can introduce all the rock at once, do
your "rockscaping", and have the tank completely set up when
introducing the first fish.
* You will have amazing growth of whatever comes
on the LR - with no fish to eat them, you will get all kinds of macro
algae, featherduster worms, soft polyps, even some corals, growing.
* You will also enable the "small life",
such as copepods and amphipods, to establish and multiply to such an extent
that they should survive predation by your fish. Obviously, if you only
have 2 or 3 of a specie to start off with, and they're eaten by a fish
on the very first day, none will multiply after that.
Disadvantages:
* You will have to wait before you introduce
any fish.
* Because the initial bio load was smaller, you
will have to add your fish at a much slower tempo to avoid causing another
ammonia/nitrite spike.
* You might have some algae growing on the LR.
This is usually not a problem, though, as you start off with a nutrient
poor set-up, which can be easily maintained, as there are no fish to feed.
Also, the growing macro algae compete for nutrients, thereby
Deep Live Sand Bed filtration:
A general rule of thumb is to have a 4"
layer of fine, graded sand, although the actual thickness would depend
on the size of the sand. The finer the sand, the less water flow is possible
between the particles, and the thinner the layer needed to achieve an
anoxic zone in the sand. IMHO the very small size sand, though "perfect"
for nitrate reduction, is not what occurs naturally, and does not allow
hiding places for many small critters. My sandbed is made up of ~75% natural
sea sand (shell grit and silicon sand, ranging from ~0.5mm to ~ 6mm in
size)) and ~25% crushed coral sand (approximately 1-2mm in diameter).
I have found that the areas containing the coarser particles have a greater
abundance of small critters.
Using Additives:
It's quite human to want to add all kinds of
things to help our creatures. The manufacturers and shops know this, and
make a lot of money out of this "weakness". Unfortunately, many
of these "snake oils" are just expensive water (perhaps coloured).
Others do add trace elements, but an excess of many of these elements
are actually detrimental to your tank (amongst other things, it tends
to make cyano and hair algae grow...).
Under normal circumstances, one should only add
buffer (to keep the alkalinity up), and a calcium supplement if/when there
are hard corals (LPS or SPS) or other calcium using life forms in the
tank. Either use one of the "balanced" two-bottle supplements,
or add Kalkwasser. If you do not have many calcium absorbing animals (such
as corals), then you probably don't need to add calcium supplements. You
then also don't need those high calcium levels normally quoted for a reef
tank.
Note that the long-term addition of calcium chloride will result in a
gradual increase of the chloride content of the water. This will eventually
result in your water's chemistry being quite different from that of natural
seawater, which is not good at all
Apart from this, I would not add any supplements
unless I could test for it, and found a deficiency, as regular partial
water changes would replenish the trace elements used up by the inhabitants.
I realise that I've only skimmed the surface of starting with
this great hobby (pun intended), but I hope that this article can be of
some use to someone out there…
Page 1 - 2
- 3
|
