Setup path, stage 10
First corals for a reef tank: when and which
Start with hardy soft corals at low light, add LPS once the numbers hold steady, and leave SPS until the tank has months of stable tests behind it. A cycled tank is ready for fish, not yet for corals.
Last checked . How we check
What do you need for this stage?
- Alkalinity test kit (calcium and magnesium for stony corals)
- A coral dip
- Frag plugs and coral glue
- A PAR meter if you can borrow one
When is a new tank ready for corals?
One guide suggests three weekly tests in a row that hold steady before the first coral (typical). We use the same idea with numbers: ammonia and nitrite zero, salinity steady, nitrate and phosphate measurable rather than zero, and alkalinity moving by less than about half a dKH over a week. Red Sea's Reef Mature says SPS can follow its 21-day programme; we would not.
Which corals are easiest for beginners?
Charterhouse lists zoanthids, mushrooms, leathers, duncans, candy canes and blastomussa. Our coral pages give light and flow for each:
- Mushroom corals, low light
- Zoanthids (handle with gloves: some carry palytoxin)
- Toadstool leather
- Green star polyps (spreads fast; keep it on its own rock)
- Duncan coral
- Candy cane coral
- Blastomussa
See all corals filtered to soft corals.
How much light do first corals need?
BRS (2025) gives about 75 to 150 PAR for soft corals and LPS, and 200 to 350 for SPS. If you have no PAR meter, start lower: place new corals low in the tank and move them up over a few weeks. BRS advises acclimatising down and then up when lights change, without giving a schedule. Keep about 10 hours a day with ramps. The light and PAR tool helps plan the hours.
What should I start testing once corals go in?
Soft corals use little calcium and alkalinity; water changes usually cover it. Once you add LPS and later SPS, start testing alkalinity two or three times a week and calcium and magnesium weekly, as Charterhouse suggests for a new tank. Reef Builders suggests dosing only once alkalinity, calcium or magnesium fall below natural seawater (about 7 dKH, 400 ppm and 1200 ppm), and logging tests daily for a week first to measure how fast they fall. The methods compared page covers what to dose with.
What are the steps, in order?
- Pass the coral gate below.
- Buy one or two hardy soft corals on frag plugs.
- Dip and inspect each for pests before it goes in.
- Place low and out of strong flow; glue the plug in place.
- Move up over a few weeks if it stays closed or stretches.
- Start alkalinity tests two or three times a week before adding LPS.
Your checklist
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What test must pass before moving on?
Ready for the first corals when, for three weekly tests in a row:
- Ammonia and nitrite read zero.
- Salinity is within 0.5 ppt of target.
- Nitrate and phosphate are measurable (not zero) and not climbing.
- Alkalinity moves by less than about 0.5 dKH across the week.
What are the common mistakes?
- Buying SPS for a three-month-old tank.
- Placing corals at the top under full light on day one.
- No dip, then finding flatworms or nudibranchs weeks later.
- Green star polyps or xenia on the main rockwork, where they spread.
- Starting a dosing pump before measuring how fast alkalinity falls.
Where do sources disagree?
| Topic | What sources say | Our reading |
|---|---|---|
| When corals can go in |
| Soft corals after three stable weekly tests; LPS after a month or two more; SPS after months of steady alkalinity, calcium and magnesium. |
| PAR for soft corals and LPS |
| Start low, about 75 to 150, and move up only if the coral asks for it. |
Sources
- Charterhouse Aquatics, a beginner reef keeper’s shopping list
- Charterhouse Aquatics, what to test in a reef aquarium and how often
- BRS, dialling in reef lighting with a PAR meter
- BRS, reef lighting guide: the right PAR for colour and growth
- BRS, best reef tank lighting schedule
- Reef Builders, how and why to dose your reef tank
- Red Sea, Reef Mature starter kit manual
Figures from sources read as a search summary only are shown as typical figures: check them before you rely on them. Found a mistake? Tell us how to fix it.