Media reactors make filtration more precise. They push water evenly through a chosen media. Used well, they can lower nutrients and improve clarity.
What a media reactor does and when to use one
A media reactor is a small canister with a pump feed. Water enters at one end and exits at the other. The goal is controlled contact time with the media.
Reactors work best for carbon, GFO, and bio pellets. Carbon removes yellowing and odors fast. GFO binds phosphate and can slow algae growth.
Use a reactor when you need stable, repeatable results. A media bag in a sump can channel water. A reactor reduces bypass and improves efficiency.
Match media choice to your test results and goals. For reefs, aim for phosphate at 0.03–0.10 ppm. Keep nitrate around 2–15 ppm for most mixed reefs.
- Use carbon for clearer water and toxin removal after coral stress.
- Use GFO when phosphate stays above 0.10 ppm despite water changes.
- Use a reactor for consistent flow instead of tumbling media in a bag.
If you are still dialing in nutrients, review your reef tank nutrient control basics. It helps you pick the right media. It also prevents overcorrection.
Setup steps: plumbing, media amount, and flow tuning
Start by placing the reactor where spills are safe. Many hobbyists mount it in the sump cabinet. Keep it upright and easy to open.
Rinse the media before use. Rinse carbon until water runs mostly clear. Rinse GFO until the brown dust stops.
Use a small pump or a manifold line. Target 50–150 gph for most small reactors. Add a valve so you can fine tune flow.
For GFO, aim for a gentle “simmer.” The top surface should barely move. Too much tumble grinds media and releases dust.
- Carbon: run moderate flow with no tumble.
- GFO: slow flow with slight surface movement.
- Check fittings for drips after 10 minutes and again after one day.
Start with smaller media doses to avoid shock. Try 1/2 the recommended amount for the first week. This is safer for SPS and LPS corals.
Route the reactor output to a high flow sump area. This helps mix water before it hits the display. It also keeps dust away from corals.
Need help choosing carbon types and change schedules? See our activated carbon in reef tanks guide. It covers grades and common pitfalls.
Maintenance, troubleshooting, and common mistakes
Change carbon every 2–4 weeks in most tanks. Heavy feeding may need two week changes. Replace GFO when phosphate rises again.
Test phosphate twice weekly after starting GFO. A fast drop can pale corals. If phosphate falls below 0.02 ppm, reduce media or flow.
Watch for channeling and clumping. Channeling happens when water cuts a path. It reduces contact and wastes media.
Clumping often comes from low flow or trapped air. Tap the reactor gently to release bubbles. Clean sponges monthly to prevent bypass.
- If water turns cloudy, you likely skipped rinsing.
- If corals retract, slow changes and test alkalinity daily.
- If algae persists, verify phosphate with a fresh reagent kit.
A common mistake is running too much GFO at once. Another is placing the output near a coral colony. Direct dust can irritate tissue.
Also check your pump intake for snails and debris. A restricted pump lowers flow and causes clumps. A quick weekly inspection prevents surprises.
For a fuller filtration plan, read our reef tank filtration guide. It helps balance mechanical, chemical, and biological tools.
Media reactors reward steady tuning and testing. Start small, measure results, and adjust slowly. With good flow and maintenance, they become a reliable nutrient tool.
Sources: Bulk Reef Supply Media Reactor Setup Guidance; Randy Holmes-Farley, Reef Chemistry articles on phosphate control; Julian Sprung, reef aquarium husbandry references.
By
