The
last two parts of this series dealt with lighting and carbon dioxide
(CO2) supplementation. This month, we'll tackle plant nutrition
and water chemistry.
You can keep plants healthy and control algae growth by the same
means. As long as lighting and CO2 are present in adequate levels
and nutrients are in their proper ranges, plant growth will be strong
while algae will barely be present. Simply put, vigorously growing
plants equal a tough time for algae.
MACRONUTRIENTS are nutrients that plants use in
fairly large quantities. They are calcium, magnesium, nitrogen,
phosphorus, sulfur, and potassium.
Calcium and magnesium will usually be present in sufficient quantities
in tap water and make up what is known as general hardness (GH).
As long as extremes of hardness are avoided, most plants will be
fine. If the water is around 4 GH or less, calcium and magnesium
may be in short supply, causing deficiencies that may lead to deformed
leaves and even a cessation of growth. There are a few plants originating
from very soft waters that cannot tolerate excess calcium and magnesium,
but most are happy with a GH of up to about 15, so most tap water
will be adequate for normal growth. Correction of extreme values
by dilution with RO or distilled water or building GH with water
reconstitution products is rarely necessary. In nature, the ratio
of calcium to magnesium is usually around 4/1 to 3/1. Very occasionally,
most or all of a water supply's general hardness will be made up
of either calcium or magnesium, leading to a deficiency of one or
the other. That's quite rare, but it does happen. If all other tank
parameters are proper and stunting and deformed leaves still occur,
consult the water company to find out the ratio and correct it if
it's out of balance.
Don’t overlook nitrogen and phosphate levels. Nitrate levels
should ALWAYS be limited to the range of 5 to 10ppm. Phosphate levels
should be around .2-.5ppm. Levels of either that are too low will
lead to problems that are just as severe if not worse than levels
that are too high. Without enough of one or the other or both, plants
become limited by the missing nutrient or nutrients and their health
is compromised. Certain types of algae (including beard and staghorn)
and cyanobacteria may then gain the upper hand. Too much nitrate
and phosphate, and a tank may become an "algae farm" of
hair algae. Tanks with lower light and carbon dioxide levels will
probably not need supplementation of either nitrate or phosphate.
As light and CO2 levels rise, however, plant growth will speed up
and necessitate their addition (high levels in the source water
may reduce this need or even negate it). The main thing to keep
in mind is that the goal is BALANCE, and not trying to restrict
nutrients at all costs or going overboard with supplementation.
Read that last sentence again. It is without question one of the
most important things to learn about keeping successful planted
aquariums.
Nitrate can be added very economically as potassium nitrate (kno3)
from a hydroponics supply store or as one of the new nitrogen supplements
made by makers of aquarium plant products. I've been using Seachem's
Flourish Nitrogen, which is a 50/50 combination of nitrate and complexed
(and therefore safe to fish) ammonium with good results. Many, if
not all plants prefer the ammonium form of nitrogen to nitrate,
so that product may give them a slight boost. I do not recommend
adding nitrogen as sodium nitrate or urea, the latter being a main
component of many fertilizers made for terrestrial plants.
A good source of phosphate is potassium phosphate. Alternatively,
you may use a commercial aquarium plant supplement. Nitrate and
phosphate additions should definitely not be approached haphazardly!
I strongly recommend doing the following. Start by getting quality
test kits for both. Test the tank water and the water you will be
using for water changes. If supplementation is required, start with
very small additions of what is in short supply and gradually increase
the amount until the target levels are reached and maintained over
time. You will soon get into a regular dosing routine and only have
to test occasionally to make sure everything is all right. With
experience, you will be able to tell if nitrate and phosphate levels
are where they should be based of plant response and what types
of algae, if any, appear. Changing light bulbs, removing large amounts
of plant matter, and so on might require starting over.
Potassium is next. When plants are growing well, making sure they
have enough potassium is very important! It plays a major part in
the biological processes of plants. If it's not present in large
enough quantities, nothing will grow as healthy and lush as it would
otherwise. Adding potassium sulfate (again from a hydroponics supply
store) works well and also supplies additional sulfur that the plants
need. Like with the other macronutrients, potassium is available
as supplements by aquarium product manufacturers. A potassium level
of 20 parts per million or so is a good level to shoot for. Finding
out potassium levels in your tap water and either dosing potassium
sulfate with web-based dosage calculators or going with a manufacturer's
recommendation for a commercial supplement are good ways to accomplish
that goal. There are few potassium tests available, and those that
are are expensive and difficult to use. Save your money for a different
kit, since it is pretty hard to overdose potassium and higher than
necessary levels are not normally something to worry about. When
in doubt as to how much potassium to add, go with more rather than
less.
MICRO NUTRIENTS are used in smaller amounts by
plants and include iron, boron, manganese, and molybdenum. While
plants don't use as many micronutrients as macros, micronutrients
are no less important. A variety of commercial supplements like
Seachem's Flourish and Tropica's Master Grow are available and work
quite well. Some people use hydroponics trace mixes with good results.
Note that most manufacturers’ dosage recommendations are conservative
and are merely starting points. Tanks that have higher light and
more plants will require more.
Iron is used by plants in larger amounts than other trace elements
and is available on its own. Adding iron in addition to the regular
micronutrient supplements helps because putting in enough trace
element additives to get the required iron level (about .1ppm) might
lead to too many traces.
I feel a few words about test kits should be helpful. Basically,
there are cheap hobbyist-grade kits and more expensive ones that
offer greater precision, reliability, and ease of use. For tanks
with lower light and CO2 levels, using an inexpensive kit that will
give you a "ballpark" estimate of how much of a certain
nutrient is present is fine. As I mentioned before, I would definitely
not go without better kits (especially nitrate) for aquariums with
higher light and CO2. Keeping a close eye on nutrient levels is
much more important in such situations. Lamotte makes a great nitrogen
kit that lets you compare the test water against water samples of
known values. It is not inexpensive, but you get what you pay for.
That doesn't really apply so much to GH and KH kits, though; so
most hobbyist-grade test kits are adequate. I use the Aquarium Pharmacuticals
kit, and I imagine most others are fine as well.
That's it for now. Stay tuned for the next spine-tingling installment
of Getting Started with Planted Aquariums! |
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