Algae in a Planted Tank
There are many different varieties of algae that appear in aquariums. I'm going
to describe the ones I know about, and also describe methods to control the
algae in a planted tank.
- Green spot algae: Hard green spots of algae. Often appears on glass, and on the
leaves of very slow-growing plants.
I mention this one first because it's the most common, and
the simple fact is, you can't do much about it. I clean my glass weekly to take
care of it. I noticed some growing on the older leaves of my Anubias coffeefolia.
To control that, I re-arranged some plants, so the slow-growing anubias doesn't get so much
direct light. This has greatly decreased the green-spot algae on the plant
Most suckermouth catfish will clean a little bit of this up. Mine occasionally check
it out, but never seem to remove much.
- Hair algae: Long green strands. Easy to pull off by hand. I've seen strands of
this stuff over 4 inches long.
Primarily a problem when there is excess iron in the water. High iron normally
results from excess fertilization, but some water supplies have high iron levels
(especially well water). When I was over-dosing my 29g tank with Seachem Flourish,
I got lots of this stuff. Reducing dosage of iron containing fertilizers completely
eliminated the problem.
I've seen my Tiger Barbs, SAEs, and Algae-Eating Shrimp all nibble at this stuff.
- Red algae: Also called Black Beard Algae (bba), or Black Brush Algae. Short
hairs (1/4" long), closely packed together. Appears dark green, black, or dark red.
Grows on plant leaves, and sometimes on decorations/substrate. Often grows all
around the edges of plant leaves.
BBA thrives in situations of high phosphates. Phosphates come from fish waste,
excess food, and occasionally will be present in the water supply. The best
way to eliminate BBA is to let the plants out-compete the algae for the nutrients.
In heavily planted tanks, BBA will often show up when the plants have used up
all the nitrates. This causes plant growth to slow or stop, which leaves the
excess phosphates available to the algae. By supplying extra Nitrate to a planted
tank, we allow plant growth to continue until all phosphate is consumed. Then
plant AND algae growth will slow/stop. As long as a usable (5-10ppm) level of Nitrate is
maintained, the the plants will continue to use up the available phosphate,
effectively controls BBA and other phosphorus-dependant algaes. See the
"Adding Nitrate to a Planted Tank" for detailed instructions on how to
increase your Nitrate levels.
Very few fish will eat BBA. The most famous one is the SAE (Siamese Algae Eater).
I've got 5 of them in my 75g. I added several BBA infested stems of Bacopa to
the tank recently, and overnight, the SAEs had completely cleaned it. But even
these amazing fish won't be able to control it you don't have the phosphate
level under control. Another fish rumored to eat BBA is the American Flag Fish.
In tanks with very large amounts of BBA, the BBA covered leaves should be removed
once the phosphate level is controlled.
- Blue-Green Algae: This is actually Cyanobacteria. Commonly referred to by the
initials BGA. BGA is a green shiny slimey algae. It's got a nasty smell to it.
It tends to grow in sheets. It is very different from most algaes. BGA is
a bizarre combination of bacteria and algae.
It is common in two different circumstances:
- In very low nitrate situations, BGA
will sometimes form. It is able to get nitrogen from the air. I've seen BGA
several times right near the surface, under the filter return. In this location,
it can obtain nitrogen from the air. Adding Nitrate to maintain a 5-10ppm nitrate
level often eliminates the BGA.
- BGA has also been found to occur in situations where poor water currents in
the tank result in low O2 levels in portions of the tank. In these cases,
increasing water movement will often eliminate the BGA.
No fish will eat BGA. As stated above, BGA is a bacteria. Some studies suggest
that BGA contains toxins. This would explain why nothing will eat it. As a last
resort, antibiotics have been used to clear BGA. But antibiotics should be used
carefully. They can damage bio-filter bacteria, and mis-use of antibiotics can be
harmfull to the fish.
- Green Water: This is a free-floating form of algae. Normally the result of
high light, and VERY high nutrient levels. There are water additives that
claim to eliminate or clear up green water problems. Water-polishing filters
also will clear the water. But these solutions don't address the original
cause of the problem: The excess nutrients. Green water can appear if
you have high nitrates, but plant growth is insufficient to reduce the nitrate
level. This can happen if you don't have enough fast-growing plants, or if
the plants don't have the CO2 needed for fast growth. Extremely high
nitrate levels, besides being harmful to the fish, reduce plant growth, and
actually increase the amount of CO2 needed by the plants.
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