Filtration in your Aquarium

There are three types of Filtration in an aquarium: mechanical, chemical, and biological.

Biological filtration

Biological filtration is the breakdown of waste products by microorganisms such as bacteria in the aquarium. Typically these bacteria live on or in the live rock or live sand, or virtually anywhere there is a surface that comes in contact with the aquarium water. This includes the plumbing and your sump.

Live rock and live sand are the best source of the beneficial type of bacteria. They will colonize these surfaces naturally. This is a natural process that will occur as your tank is "cycled". Once the population of bacteria is large enough, it will suppport changes in the numbers of fish or coral.

For a detailed discussion on how to colonize these beneficial bacteria, visit our section on Cycling your Aquarium.

Mechanical filtration

Feather Dusters (pictured left), such as these in one of our sumps at our farm, can grow in your aquarium or sump and act a live filter to mechanically remove particulates from your system.

Mechanical Filtration typically uses some form of filter pad to capture waste debris particles. Usually water is allowed to flow through the pad, but dirt and detritus will be caught in the pad since they are larger particles than a water molecule.

The main consideration in choosing the right material is the pore size, you know what size allows through because all we down the even 1 µ and all the way up. If you are building your own filter from scratch, start off filtering out the largest particles first and work your way down consecutively to smaller and smaller particles. The final filter in the chain is the smallest pore size.

The filter would get clogged up very, very quickly if you didn't filter out the larger particles. Three layers at least should be used. In order they are : largest pore size, medium pore size, and smallest pore size.

And it is very important to clean these mechanical filters often, at least weekly. Trapped particles will decay and just pollute your tank. That's why we DON'T recommend wet/dry filters anymore.

Chemical filtration

Chemical Filtration uses resins or carbon to breakdown the waste products from toxic to non toxic forms. For us, resins are not necessary, but we do recommend the use of Carbon so be sure to check out that section.

Ok so which of these 3 do we recommend in SPS and Soft coral systems?

Soft Coral Filtration

In our experience, the best type of filtration for soft corals is using live rock and live sand, and possibly a mud/macroalgae filter. There is no need for mechanical filtration. If you do start to get an algae problem, then you should suction up as much detritus as possible. But running a full time mechanical filter will just add pollutants back to the water stream if its not cleaned often.

Soft corals like a higher nutrient load, and some suspended particles and detritus will benefit the coral as long as hair algae isnt present. In fact in our soft systems, we feed them VERY heavily. I am always thinking if we keep feeding them this much, that at least SOME hair algae should show up. But we have ZERO hair algae in our soft systems. I think the soft corals use up the nutrients and the grazers (tangs and urchins) keep any algae that does pop up under control.

SPS Coral Filtration

In our experience, the best type of filtration for an SPS system is actually just lots of high quality live rock and no sand bed to trap detritus. We don't feed our fish in our SPS systems any flake or protein foods. In fact the only fish we have in there are vegetarians. So we add some Nori often but that is all. Since it is vegetable matter, it doesn't really add to the dissolved organic load of the water. So no food = no source of pollution! SPS don't seem to need the heavy organic loaded water that soft corals do. They just need the high calcium and alkalinity levels we talk about elsewhere.