When you talk
about algae in the marine aquarium, you are most likely talking
about 'problem algae' (micro-algae) rather than the 'plants'
(macro-algae) that look good in the aquarium. This article
is a look at controlling problem algae in your marine aquarium.
It is purposefully brief, and is aimed primarily at 'fighting
the fire'. A longer in-depth article does exist called 'Marine
Algae Overview' that has a lot more information on algae and
its use in a marine aquarium.
There are three types of algae, in order, that I consider
problem algae. These algae are going to find their way into
your tank. Their spores will reach your tank from the air
or from the water your livestock or foods come in. You cant
stop them getting into your tank.
This grows in mats, and looks like fine hair (thus the name),
it can grow over rocks, other substrate, glass, pumps, pipes
- basically anything in the tank.
This is a greasy alga in red, green or black varieties. It
covers rocks and substrate.
Is very fast growing brown film that grows on the glass especially
in aquariums with strong lighting.
There is never a single causal component to algae affecting
an aquarium. Rather, it is a combination of factors. These
include water quality (phosphates, nitrates & ammonias),
accumulation of detritus, lighting, and supplements.
Phosphates: Any measurable level
of phosphate can cause algae problems, as it is a primary
food source for the algae. Levels of phosphate should be kept
as low as possible.
Nitrate: Is another food source
Ammonia: Algae can take up ammonia
directly from the water.
Detritus build up: Pockets of
sediment are often the first place algae get footholds. Hair
algae specifically seem to 'trap' detritus and then utilize
this for further growth.
Lighting: Bright lights with
a long photoperiod will help algae grow. Additionally old
lights shift to the red end of the light spectrum as they
age, encouraging algal growth.
Supplements: Only use supplements
if you are sure that they will benefit your aquarium inhabitants.
A combination of the above is the likely cause of your algae
How to get rid of problem algae
Once you realize you have an algae problem, things need sorting
out as fast as possible. The problem will not go away as quickly
as it arrived, but you can keep it under control.
What are you putting into your tank? Check to see if you
can reduce the food you are adding to the tank. Eaten and
uneaten food becomes algae food! Check the quality of your
food. Are you dumping a frozen cube into the tank? A lot of
the cube is 'dirty' water and bits of shrimp that the seahorses
will not eat, but immediately becomes a food source for the
algae. Rinsing the food will reduce the effluent from fouling
First, start the mechanical removal of as much algae as you
can get your hands on. This is the initial major clean up.
During this time it will help to add filter floss or filter
wool as the first stage in your filter - to capture the pieces
of algae dislodged by your clean up, but not removed from
the water. Make sure you clean or replace this filter regularly
in the first few days. Check the condition of your filter
at the same time and clean as needed.
Next, check your water flow. See if there are any 'dead-water'
areas, in which algae can get a foothold.
Vacuum the substrate to remove as much detritus as possible.
The water removed from the tank should be replaced with new
seawater from a source that does not contain phosphates or
nitrates, such as reverse osmosis (RO) water. A 20% water
change is most beneficial.
If your photoperiod is more than 12 hours, consider lessening
it. Replace any bulbs over six months old as the spectrum
emitted shifts over time to light emissions that promotes
Now attempt to improve the water quality. Adding commercial
products to the filter is the first line of attack to improving
the water quality quickly:
Polyfilter - Available as a pad.
You can cut it to shape to fit your filter. Add the Polyfilter
as the LAST stage in the filter - before the water returns
to the tank. Polyfilter removes dissolved organics, minerals
as well as some phosphates and nitrates.
Phosphate remover - There are
several commercial products available to remove phosphate
from the water. Most are in the form of a powder which is
added to a filter. Place this second last in the filter, before
the Polyfilter. You have to be cautious, as some types leach
the phosphate back into the water after removing it. Read
the instructions! I use Rowaphos which is
the best product I know of for removing phosphate. This product
also reduces silicate - which is a contributing cause to Diatomic
Next thing to consider is the 'cleaning
crew' or animals that eat/control alga. Dumping a cleanup
crew into the tank is not an answer by itself. They will not
be able to deal with an outbreak caused by poor maintenance,
and most cannot deal with established algae problems. They
are however a useful tool in the ongoing control of problem
algae. I follow the general recommendation of one red leg
hermit and one turbo or astrea snail per five gallons of aquarium
water. Having cleaned the major patches of algae out of your
tank, your cleanup crew should be able to assist in keeping
any future outbreaks under control.
Lights are a problem area. If
you have corals, you will need the lights, but if you have
a fish only tank, you can turn off the lights for a few days.
The fish will not mind, accepting the ambient light, but the
algae will not be happy. Even tanks with corals can do with
a break from the lights. If you have corals try reducing the
Finally, Macro-Algae - using
algae to control algae! Macro algae is the 'plant' and encrusting
algae that you see in marine tanks. Macro algae cut down on
light available to the micro algae, and compete directly for
the nutrients otherwise available to problem algae. Caulerpa
spp and encrusting corallines (a group of Red algae resembling
corals) are best. Encrusting corallines produce chemicals
that stop the growth of micro-algae on rocks etc. Caulerpa
is a fast growing green macro-algae, and commonly available.
Another less commonly used method is that of mangrove
plants, whose roots extract the nutrients micro-algae
would need for growth. These however take several months to
become effective, and success stories vary.
Continuation of the fight.
Whilst you are fighting the outbreak, you should change
a minimum of 10% of the water every week, siphoning out as
much detritus & algae as possible. Remember to keep cleaning
the mechanical filter media as soon as it becomes soiled.
This is an indicator of the success you are having in the
tank. Check and change the Polyfilter as soon as it becomes
At this time the algae bloom should be under control. However,
it is still important that your carry out the maintenance
to prevent the algae from returning.