Small reef tanks can grow stunning coral. They can also stall fast. The key is stability, then targeted tweaks.
Start with stability: light, flow, and core parameters
In a nano reef, swings happen fast. Keep salinity at 35 ppt (1.026). Hold temperature at 25–26°C (77–79°F). Use an ATO to stop daily salinity creep.
Match light to coral type and tank depth. Aim for 80–150 PAR for most LPS. Target 150–250 PAR for many SPS. Start lower and ramp up over 2–3 weeks. Use an 8–10 hour peak photoperiod.
Flow drives growth and prevents dead spots. Use 20–40x turnover per hour as a guide. Make flow random and indirect. Keep fleshy LPS from whipping in strong jets. Keep SPS tips from collecting detritus.
Lock in alkalinity, calcium, and magnesium. Keep alkalinity 7.5–9.0 dKH. Keep calcium 400–450 ppm. Keep magnesium 1250–1400 ppm. Test alk 3–4 times weekly in new tanks. See reef tank water parameters for target ranges.
- Change 10–15% water weekly in tanks under 20 gallons.
- Calibrate refractometers with 35 ppt solution, not RO water.
- Clean pump intakes weekly to keep flow consistent.
Feed the reef: nutrients, dosing, and real-world routines
Corals need some nutrients to grow. Ultra-low nutrients can pale coral. High nutrients can brown coral. Aim for nitrate 2–15 ppm and phosphate 0.03–0.10 ppm. Use consistent testing, not guesses.
In small tanks, dosing is safer than chasing numbers. If alkalinity drops more than 0.3 dKH per day, start dosing. Use a two-part or all-in-one. Dose daily in small amounts. Re-test after three days and adjust slowly.
Feed fish to feed corals, but do it on purpose. Offer small meals twice daily. Use a mix of pellets and frozen. Rinse frozen food to reduce phosphate spikes. For LPS, spot feed once or twice weekly. Use tiny portions and turn off pumps for 10 minutes.
Example routine for a 15-gallon mixed reef helps. Do 2 gallons weekly water change. Test alkalinity on Monday, Wednesday, and Saturday. Dose 2–5 ml per day based on demand. Adjust light intensity by 5% per week only.
- If nitrate hits 0, feed more or reduce skimming time.
- If phosphate hits 0, consider a lighter GFO schedule or none.
- If algae blooms, cut feeding by 10–20% and increase export.
Troubleshooting slow growth in nano reefs
Slow growth often comes from instability, not “bad coral.” Look for daily temperature swings over 1°F. Check for salinity drift from manual top-off. Confirm test kit accuracy with a known reference. Review your last two weeks of logs.
Watch for chemical warfare in tight spaces. Soft corals can suppress SPS growth. Run fresh carbon in a mesh bag. Replace it every 2–4 weeks. Consider spacing aggressive corals farther apart. Use a small powerhead to keep mucus from settling.
Check for hidden pests and irritation. Flatworms and nudibranchs slow growth. Inspect at night with a flashlight. Dip new frags and quarantine when possible. Use coral quarantine setup steps for safer additions.
Common mistake is changing many things at once. Avoid big alkalinity jumps. Keep changes under 0.5 dKH per day. Avoid sudden light increases. If a coral browns, reduce nutrients slowly. If it pales, raise nutrients and lower light slightly. For more ideas, see nano reef care guide.
- Target alkalinity stability before chasing higher PAR.
- Blow detritus off rock twice weekly with a turkey baster.
- Replace old bulbs and clean lenses to restore output.
Small reef tanks reward patience and consistency. Keep parameters stable and changes small. With steady light, flow, and nutrients, coral growth will follow.
Sources: Randy Holmes-Farley, “Alkalinity in Reef Aquaria”; Dana Riddle, “PAR and Coral Lighting”; Borneman, “Aquarium Corals”.
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