Phytoplankton dosing is one of the simplest “small habits” that can make a big difference in reef stability—especially if you keep copepods, run a refugium, or want stronger polyp extension. The key is to dose with a purpose: feed the parts of the food web that you can’t hand-feed directly (pods, filter feeders, and microfauna), while avoiding the classic mistake of turning phyto into excess nutrients.
What phytoplankton actually does in a reef tank
- Feeds pods: Copepods and other microfauna consume phytoplankton, then become live food for fish and corals.
- Supports filter feeders: Many corals, sponges, feather dusters, and bivalves benefit from a steady plankton background.
- Strengthens refugium performance: A well-fed refugium tends to export nutrients more predictably because the ecosystem is “alive,” not starving.
When to dose (simple schedule that works)
You can dose phytoplankton any time, but most reef keepers get the best results when they dose consistently and match dosing to animal behavior.
- Night dosing: Great for pods and many corals that extend feeding tentacles after lights out.
- Split dosing: Smaller doses more often (instead of one big dump) reduces nutrient spikes and keeps a steadier plankton background.
- Refugium-first dosing: If you have a refugium, dosing there helps pods reproduce and “seed” the display naturally.
How much to dose (use these checkpoints)
There is no single perfect number because every tank has different filtration, livestock, and pod pressure. Instead, dose based on observable checkpoints:
- Checkpoint 1: Water tint — A light green tint that clears within several hours is usually a good sign.
- Checkpoint 2: Pod visibility — More specks on the glass at night and increased activity in the refugium are good indicators.
- Checkpoint 3: Nutrients — If nitrate/phosphate trend upward week over week, reduce dose or increase export.
Overfeeding vs underfeeding (quick chart)
| What You Notice | Likely Cause | Adjustment |
|---|---|---|
| Water stays green for 12–24+ hours | Overdosing / low consumption | Cut dose by 25–50% and/or split into smaller doses. |
| Pods not increasing over weeks | Underfeeding pods / heavy predation | Increase dose slightly and consider adding pods to refugium. |
| Rising nitrate/phosphate | Too much input vs export | Reduce phyto dose or improve export (macroalgae, skimming, water changes). |
| Better polyp extension after dosing | Good feeding window | Keep schedule consistent; consider split dosing. |
Best practices for clean dosing
- Dose into high flow: Add phyto near a return outlet or powerhead so it distributes quickly.
- Start low and ramp up: Let your system “show you” what it can process.
- Keep it cold and fresh: Store phytoplankton as instructed and avoid leaving bottles warm for long periods.
- Match dosing to goals: Heavy pod tanks and larval systems usually need more frequent dosing than fish-only reefs.
Featured dosing helpers
Bio-actiV Freshwater Plankton™ — Easy, consistent plankton nutrition to support microfauna and feeding routines.
Zoo-Plasm™ PODS — A convenient plankton option that pairs well with live-food and pod-support routines.
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