What is Filtration?

• Mechanical:

  This process screens out floating debris from the water.  Some examples are sponge filters and corner filters with filter wool.  The one or more layers of the filter medium create a straining device through which the water passes and floating organic waste is removed from the water before it has a chance to decay and pollute.  This medium has to be replaced or maintained by cleaning on a regular basis to prevent waste from re-entering the aquarium environment.

• Chemical:

  These remove colour producing chemicals and odours from the water.  There will be times when chemical additives are needed in your tank.  These initiate various chemical reactions to remove heavy metal irons, change the pH, add hardness or remove carbonates to soften the water.  These will be determined as your check your water parameters and should be adjusted when necessary.

• Biological:

  Biological Filtration uses a process known as the Nitrogen cycle - the removal of organically produced nitrogenous wastes by bacterial action.  Basically this process uses beneficial bacteria to convert toxins like ammonia into relative harmless substances.  All marine tanks need biological filtration.  Bio-filters used with some form of mechanical filtration are the best form of filtration for a seahorse tank.

What Sort Of Bio-Filter Should I Use?

• Under-Gravel Filters:

  These use a moulded plastic plate to cover the entire bottom of the aquarium.  This elevates the gravel bed.  Return tubes connected to the plate support air lift pumps assemblies or power heads.  Water is drawn through the gravel under the plate and returned to the aquarium.

  The actual bio-filter medium is the gravel itself.  A good flow of oxygenated water is required to keep all your nitrifying bacteria alive.  Crushed shell/coral can be used in place of gravel.  These types of filters are not very popular with most seahorse enthusiasts, although many have used them when keeping dwarf seahorses and still do.

• Submersible Filters:

  These filters can incorporate a power head.  The water flows can create strong currents, which suspend debris for efficient capture.  These internal filters usually contain a cartridge insert, which combines mechanical filtration (removal of debris) and biological filtration medium (removal of toxins like ammonia and nitrite).  These are probably the most popular and reliable form of filtration.

  Some submersible filters can be operated by air pumps examples are foam filters and corner filters.  These filters work well in small aquariums with only a couple of small seahorses.  The nitrifying bacteria attach to the foam, or other filtration medium, some even incorporate carbon.

• External Power Filters:

  An internal pump draws the water from the aquarium via plastic tubing and pumps it through the filter, which could be an external canister or sump set-up containing filter medium.  The water flows through this medium and then travels back into the tank.  This added water movement also aids in aeration.

  These come in varying sizes and again advice should be sought as to the size your tank requires.  It is recommended to cycle your water through the filter at least twice per hour, three times would be even better.  Your aquarium shop will need to know the volume in litres and dimensions, height and length to calculate the pump that suits you best.  These are also popular and work well.

  Even though a pump may say it can pump 250 litres per hour, remember that you are adding resistance to flow.  This pump may only pump 50 litres per hour because the water has to flow through your filter medium and the inlet/outlet tubing.

Biological Filtration - The Nitrogen Cycle

Invisible toxins like ammonia and nitrite are transformed into relatively harmless substance nitrate by the bacteria Nitrosomonas sp. and Nitrobacter sp. respectively.  These are commonly referred to as "nitrifying bacteria".  These aerobic (require oxygen to live) bacteria attach to surfaces such as gravel, glass, rocks, filter panels, sand and filter media, the more surface area you have the more bacteria can grow.

Like all fish, seahorses create ammonia as they breathe, in excreta and urine, the decay of plant matter and uneaten food caused by overfeeding also causes ammonia.  Ammonia is deadly to all fish.  The Nitrogen cycle can take 3-6 weeks to be working efficiently.  It is important to monitor the ammonia, nitrite and nitrate levels during this cycle period.

As a result of the ammonia build up, Nitrosomonas bacteria absorb the ammonia and transform it into energy for themselves and produce the by-product nitrite.  Although slightly less toxic than ammonia high concentrations of nitrite (which do occur in the initial set up) can prove fatal to seahorses.

When the nitrite concentrations are increased thanks to the activity of the Nitrosomonas bacteria, the other beneficial bacteria Nitrobacter use the nitrites as an energy source.

Nitrite is then transformed into nitrate.  While in high concentrations nitrate is lethal, low concentrations ensure proper biological filtration is occurring.

Without biological breakdown of toxins the seahorses will literally poison themselves.  These beneficial bacteria will grow as your tank ages.  You can start a biological filter going by adding products containing these bacteria.  You should not use fish to start your bio filter.

Products like Bio-start or similar are available.  Ensure you read all directions carefully.  You will have to feed your stockless tank some form of ammonia every day for the cycling period.  A small amount of fish flake food is fine.

You will need to test your aquarium every couple of days.  Your ammonia levels will be the first to rise.  As the first nitrifying bacteria acts you will notice what is called a nitrite spike and you will have high nitrite levels (as high as 4.0 ppm).

You will notice these levels lessen and you should by the fourth or fifth week be getting nil ammonia readings (0.0 ppm), nil nitrite levels (0.0 ppm) and readings of between 20 ppm to 40 ppm of nitrates.

Once the above readings have been achieved, your bio-filter is active and you can introduce your seahorses to the tank.

Bio-Filter Mediums:

The most expensive does not necessarily mean it's the best.  Some large hatcheries use a variety of mediums like oyster shells, crushed coral/shells and gravel.

Your bio filter will only ever have the ability to cope with the current bio-mass of your tank.  Bio-mass is the body weight of the seahorses in your tank.  For example if you have four seahorses in a tank weighing 50 grams each, that is the current bio-mass capacity of your biological filter (200 grams).

If you decided to add another 6 seahorses to that tank, your bio-filter would not cope, you would experience high ammonia levels, followed by a nitrite spike, this will be harmful and cause stress to your seahorses.  To add more tank mates you would need to add them slowly and give your biofilter time to adjust.  Only ever add one or two more at a time.

During these times a close check on parameters such as ammonia, nitrite and nitrate should be maintained.  Regular water changes (20-30%) help keep these levels below danger levels.  You should not add seahorses to any tank that has not been cycled for at least four weeks.  Although they are hardy, living in toxins for several weeks is cruel and the chances are they will die.

Cleaning your filters:

Mechanical filters need to be cleaned weekly by rinsing the filter medium in clean salt water.  When the mechanical filter gets blocked it should be replaced.  Accumulation of debris will not only cut back on the effectiveness of your bio filter but will add more resistance to flow (the water flow rate going through your filter will be substantially reduced).  If you wash in tap water you will kill off those beneficial bacteria and have to start all over again.  Be gentle and watch and monitor ammonia, nitrite and nitrate spikes.  Once again regular water changes (20-30%) will help to keep these levels below the danger levels until your biofilter gets back on track.