Salt Water Fish

It is more demanding on equipment and water chemistry. You need a protein skimmer, refractometer, RO/DI water and stable salinity around 1.025 SG. The biological processes are the same, but the margin for error is tighter — calcium, alkalinity and magnesium all matter once corals are involved.

A pair of captive-bred Ocellaris or Percula clownfish can thrive in a 60–75L nano reef. Larger clownfish like Maroons need 200L+. Always cycle with live rock for 4–8 weeks before adding fish and keep salinity at 1.024–1.026 SG.

Yes, in almost every UK region. Tap water carries nitrates, phosphates and copper that fuel algae and stress invertebrates. A reverse-osmosis unit or buying RO water from a dedicated aquatics retailer is essential for mixing saltwater and for top-ups that replace evaporation.

Budget 4–8 weeks, longer if you are using dry rock rather than live rock. Test ammonia, nitrite and nitrate weekly and wait until ammonia and nitrite read zero while nitrate is present. Adding fish before the cycle completes is the main reason new marine tanks fail.

Yes, in a reef tank, but compatibility matters. Reef-safe fish like clownfish, gobies, wrasses and small tangs leave corals alone. Angelfish, butterflyfish and triggers often nip at coral polyps. Always research each fish's reef-safety before adding to a coral-focused tank.