In-Sump High Output UV Sterilizer - IceCap

Keep your aquarium water crystal clear and healthier with the IceCap In-Sump UV Sterilizer. Designed for saltwater, freshwater, and even pond use, this high-output UV sterilizer helps control and eliminate free-floating algae, bacteria, parasites, fungi, and protozoa, without the use of harsh chemicals. By reducing harmful microorganisms in the water column, it enhances water clarity, improves redox balance, and supports stronger immune function in fish and corals.

Built for ease of use, the IceCap In-Sump UV comes complete with secure mounting brackets, molded hose barbed fittings for flexible hose connections (1/2”, 3/4”, or 1”), and reliable high-output ballasts for consistent performance. Unlike permanent installations, this is a true plug-and-play sterilizer, complete with a properly sized feed pump—making setup and maintenance simple. The drop-in sump design means you don’t need complicated plumbing, and quick access to the lamp ensures stress-free replacements.

Best of all, while the IceCap UV is highly effective at killing suspended pathogens and microorganisms in the water, it does not harm beneficial bacterial colonies growing on your filtration media, substrate, or surfaces.

Key Benefits:

• Kills free-floating parasites, bacteria, algae, fungi, and protozoa

• Improves water clarity and overall aquarium health

• Plug-and-play installation with included feed pump

• No chemicals or additives required

• Safe for beneficial bacteria in filter media and substrate

• Secure, flexible mounting options with included brackets and fittings

Available Models:

IceCap In-Sump 18W UV Sterilizer (Ideal for All-In-One Aquariums)

• Freshwater up to 600 gallons

• Saltwater up to 60 gallons

• Dimensions: 3.5” x 3.5” x 18.4”

• Pump: DC-700 (included)

• Lamp Life: 10,000 hours

IceCap In-Sump 27W UV Sterilizer

• Freshwater up to 1,300 gallons

• Saltwater up to 140 gallons

• Dimensions: 4.6” x 4.3” x 22”

• Pump: EVO 1000 (included)

• Lamp Life: 10,000 hours

IceCap In-Sump 40W UV Sterilizer

• Freshwater up to 3,000 gallons

• Saltwater up to 400 gallons

• Dimensions: 5.4” x 5.1” x 24”

• Pump: EVO 2000 (included)

• Lamp Life: 10,000 hours

IceCap in-sump UV sterilizer sizing guide

Choose the wattage by total system volume, including the sump, and by what you want the UV to do. IceCap rates each model for marine and freshwater systems, and every model ships with a matched feed pump, so water reaches the lamp without any extra plumbing.

The 18W is the size IceCap recommends for all-in-one aquariums. The 27W suits most mid-size reef systems, and the 40W covers larger systems or a tank sitting near the 27W limit. Check height before you order: the units stand 18.4, 22 and 24 inches tall, the top must stay above the water line, and you need room above the unit to lift the lamp out.

Flow rate for algae control vs. parasite control

A UV sterilizer only treats the water that passes through it, so flow rate decides what it can do. IceCap's guidance:

• Green water, bacteria and free-floating algae: pass 3 to 4.5 times the system volume through the UV every hour. On a 50-gallon system that is 150 to 225 GPH.
• Ich, flukes and other parasites: use 50 to 75% less flow so organisms spend longer in front of the lamp, about 0.5 to 1.5 turnovers per hour. On a 50-gallon system that is 25 to 75 GPH.

UV reaches only free-swimming organisms in the water column. It cannot treat a parasite already attached to a fish, so use it as a preventive layer alongside quarantine rather than as a cure.

How to install an in-sump UV sterilizer

1. Push the feed pump outlet into the bottom of the UV housing.
2. Seat the quartz sleeve, connect the lamp to the ballast socket and slide the lamp into the sleeve without touching the glass with bare hands.
3. Hand-tighten the ballast nut. On the 27W and 40W, add the included downpipe and output elbow (no glue needed) and aim the outflow.
4. Set the unit in the sump so the top stays above the water even when the return pump is off and the sump level rises.
5. Mount the power supply away from water and plug the UV into a grounded, GFCI-protected outlet. The ballast beeps on start-up and shows a green light while running.

The unit is built to sit in the sump but is not fully submersible. Never look at an operating UV lamp, and unplug the unit before any maintenance.

In-sump vs. inline UV sterilizers

An in-sump UV sits in the sump with its own feed pump, so there is no plumbing to cut into and it moves easily to a new system. An inline UV is plumbed into a pump line instead, which keeps it out of the sump but means adding fittings and a dedicated loop or manifold. If sump space is tight, compare the external IceCap High Output UV Sterilizer.

Lamp and quartz sleeve replacement

Each lamp is rated for 10,000 hours, a little over a year of continuous running. UV output drops as the lamp ages and as mineral film builds on the quartz sleeve, so IceCap recommends replacing the lamp and sleeve together about once a year. Faster algae growth on the glass and rock is the usual sign it is time. Top Shelf Aquatics carries the IceCap replacement UV bulb and IceCap replacement quartz sleeve in 18W, 27W and 40W sizes.

If the ballast shows a red light and alarms when plugged in, check that the lamp is fully seated in its socket. If the alarm continues, the lamp usually needs replacing.

Choosing a UV sterilizer

This IceCap unit mounts inside the sump, which keeps plumbing simple where space allows. For an external inline alternative with a larger body and longer dwell time, compare the Aqua Ultraviolet 57 Watt Classic. Browse all UV sterilizers and the IceCap range.