Although UV sterilisers and media reactors are both used in aquarium filtration systems, they perform very different jobs.

UV sterilisers expose water passing through the unit to ultraviolet light, helping reduce susceptible free-floating algae, bacteria and certain parasite stages. They're particularly useful for managing green water and reducing some waterborne microorganisms.

Media reactors pass water through filtration materials such as activated carbon or phosphate removers. These materials remove particular dissolved substances from the water rather than targeting microorganisms.

UV sterilisers don't remove nitrate or phosphate, while conventional media reactors don't sterilise aquarium water.

Both can be useful, but neither is essential for every aquarium. The right choice depends on the problem you're trying to solve.

Yes, but their effectiveness depends on the type of algae and what's causing it to grow.

UV sterilisers can help control free-floating algae responsible for green water. However, they won't directly remove nuisance algae growing on rocks, glass or other aquarium surfaces.

Phosphate reactors use media such as GFO or Rowaphos to remove phosphate from the water. Reducing excessive phosphate can help manage conditions that encourage nuisance algae growth, although phosphate is also an essential nutrient for corals.

Algae reactors grow desirable macroalgae, such as Chaetomorpha, which absorbs nitrate and phosphate as it grows. Regular harvesting removes these nutrients from the aquarium.

None of these methods guarantees an algae-free reef. Lighting, feeding, biological balance and regular maintenance all play important roles in controlling unwanted algae.

Not necessarily! Many marine aquariums run successfully without UV sterilisers or dedicated reactors.

Your aquarium's biological filtration, protein skimmer, water changes and regular maintenance may already be sufficient to maintain good water quality.

Additional equipment becomes useful when you have a particular reason to use it.

For example, a UV steriliser may help manage persistent green water or reduce some free-floating pathogens. A phosphate reactor can help address consistently elevated phosphate, while an algae reactor offers another way to export excess nutrients.

Rather than adding equipment simply because it's available, start by understanding your aquarium's water parameters and what you're trying to improve.

Regular testing and observing your fish and corals will help you decide whether additional filtration is worthwhile.