The three coral groups that fill a typical reef tank (soft, LPS, SPS) come from different reef environments and have different care needs. Soft corals tolerate wide parameter ranges and beginner mistakes. LPS need stable alkalinity and moderate light. SPS demand pristine water with rock solid parameters within tight tolerances. A reefer who understands the difference can stock a mixed reef successfully. A reefer who treats all corals the same loses SPS within 60 days while soft corals continue to thrive. This guide covers the light, flow, parameter, and feeding requirements for each group plus the placement strategy that lets all three live together.
The three coral groups defined
Soft corals (Alcyonacea). No calcified skeleton. Bend and flex with flow. Includes mushrooms (Discosoma, Rhodactis), leather corals (Sarcophyton, Sinularia), zoanthids and palythoa, xenia, and gorgonians. Most resilient group. Suitable for first reef tanks. Survive parameter swings that kill SPS.
Large polyp stony (LPS). Calcified skeleton with large fleshy polyps. Includes hammer (Euphyllia), frogspawn (Euphyllia divisa), torch (Euphyllia glabrescens), acan (Acanthastrea), favia, blastomussa, and chalice. Moderate parameter demand. Consume alkalinity and calcium at measurable rates. Many species feed directly on mysis and pellets.
Small polyp stony (SPS). Calcified skeleton with tiny polyps covering branched or plating colonies. Includes Acropora, Montipora, Stylophora, Seriatopora, and Pocillopora. Strict parameter requirements (alk swing under 0.5 dKH per day). High light and flow demand. Sensitive to phosphate, nitrate, and temperature swings.
Light requirements (PAR targets)
PAR is the unit reefers use for usable coral light, measured in micromoles of photons per square meter per second. Different corals evolved at different reef depths and have different PAR tolerances.
Soft corals: 50 to 150 PAR.
- Mushrooms: 30 to 100 PAR. Brighter light bleaches them.
- Zoanthids and palythoa: 75 to 200 PAR (mid range is ideal).
- Leather corals: 100 to 200 PAR.
- Xenia: 50 to 150 PAR.
LPS: 100 to 250 PAR.
- Hammer and frogspawn: 100 to 200 PAR.
- Torch: 150 to 250 PAR.
- Acan: 75 to 150 PAR (these prefer lower light).
- Chalice: 75 to 175 PAR.
SPS: 200 to 450 PAR.
- Montipora: 150 to 300 PAR.
- Acropora: 250 to 450 PAR (the upper end).
- Stylophora and Pocillopora: 200 to 350 PAR.
- Seriatopora: 175 to 300 PAR.
A practical 24 inch deep reef tank uses an LED fixture (AI Hydra 32, Radion XR15 G6, Kessil A360X) that produces 250 to 400 PAR at the surface. PAR drops to 50 to 100 at the substrate after passing through 20 inches of water. That natural attenuation creates the zoning needed for mixed reefs.
Flow patterns each group needs
Flow is the second most important coral variable after light. It delivers nutrients, removes waste, and prevents detritus from settling on coral tissue.
Soft corals: gentle to medium flow (10x to 20x tank volume per hour total). Direct laminar flow tears off polyps from xenia and mushrooms. Indirect random flow from a small powerhead suits soft corals.
LPS: medium flow (20x to 30x per hour). Most LPS have tentacles that should sway, not whip. A hammer coral with tentacles pinned back is in too much flow. Move it. A hammer coral with tentacles fully extended and gently moving is happy.
SPS: high random flow (40x to 60x per hour). SPS need flow to prevent dead spots and tissue suffocation. Multiple powerheads on alternating timers (gyre flow, pulsing wave mode) suit SPS. A single steady laminar flow leaves dead zones on the back of branching colonies.
Use multiple smaller powerheads on alternating modes rather than one large pump for SPS. Tunze Nanostream 6105, Maxspect Gyre XF330, and Ecotech VorTech MP10/MP40 all do reef tank flow well.
Parameter requirements
All three groups share salinity (1.025 to 1.026 SG) and temperature (76 to 80 degrees Fahrenheit) targets. The differences are in alkalinity tolerance and nutrient sensitivity.
Soft corals. Tolerate alkalinity 6.5 to 12 dKH. Tolerate phosphate 0.02 to 0.5 ppm. Tolerate nitrate 1 to 25 ppm. Forgiving group.
LPS. Prefer alkalinity 8 to 9.5 dKH with stability under 0.5 dKH variance week to week. Phosphate 0.03 to 0.1 ppm. Nitrate 2 to 10 ppm. Sensitive to alkalinity spikes from overdosing.
SPS. Demand alkalinity 7.5 to 8.5 dKH with variance under 0.3 dKH per day. Phosphate 0.02 to 0.07 ppm. Nitrate 1 to 5 ppm. SPS coloration improves at low (but not zero) nutrients with stable alkalinity.
A two part dosing system (B-Ionic, ESV, Aquaforest) replenishes alkalinity and calcium that LPS and SPS consume. For tanks running 8 to 10 SPS colonies, alkalinity drops 0.5 to 1.5 dKH per day, requiring continuous dosing rather than daily manual doses.
Feeding
Soft corals. Rarely need feeding. Some uptake dissolved organics from fish waste. A weekly broadcast of phytoplankton or amino acids is the maximum any soft coral needs.
LPS. Benefit from targeted feeding 1 to 2 times per week. Hammer, frogspawn, and torch catch frozen mysis or pellet food in their tentacles. Acan and chalice open feeding tentacles when target fed with reef roids or LPS pellets. Direct feeding accelerates growth and coloration.
SPS. Take in dissolved nutrients and light. They cannot catch large food particles. Weekly amino acid dosing (Brightwell Aminomega, Acropower) boosts coloration. Phytoplankton dosing every 2 to 3 days supports filter feeders.
Placement strategy for a mixed reef
A 50 to 90 gallon mixed reef with all three groups uses vertical zoning:
- Upper third of rockwork (top 8 inches): SPS frags and colonies. Montipora plates, small acropora frags, stylophora.
- Middle third: LPS colonies on small ledges. Hammer, frogspawn, torch arranged so polyps do not touch (LPS sting each other).
- Lower third and sand bed: Soft corals. Mushrooms on shaded rock work, leather corals at the back, zoanthids on isolated rock islands to prevent crowding.
Leave 4 to 6 inches between any two coral species. Many corals sting neighbors with sweeper tentacles or chemical warfare that necrose adjacent colonies overnight.
Dipping new corals (mandatory step)
Every new coral coming into the display tank gets a 10 to 15 minute dip in Coral RX, Bayer Advanced complete insect killer (1:30 ratio), or Two Little Fishies ReVive. Steps:
- Acclimate the coral to display tank temperature (15 minutes floating)
- Move to dip container with diluted dip solution
- Agitate water gently to dislodge pests
- Swish coral for 10 to 15 minutes
- Inspect for flatworms, eggs, nudibranchs, and aiptasia
- Rinse in clean saltwater (separate container)
- Place in display
A skipped dip introduces pest populations that take 6 to 18 months and significant frag losses to control.
See our marine tank cleaning crew for the invertebrates supporting coral health, and reef tank starter species for the easiest first corals. The /methodology page documents our parameter testing protocols.
Frequently asked questions
Can I keep soft corals, LPS, and SPS in the same tank?+
Yes, but the tank layout must separate them by light and flow zones. SPS go on the upper rock work (200 to 400 PAR, high flow). LPS go in the middle (100 to 200 PAR, medium flow). Soft corals go on the lower rocks and substrate (50 to 150 PAR, low flow). The 90 gallon reef configurations that succeed at all three follow this vertical stratification.
What PAR reading should each coral group get?+
Soft corals: 50 to 150 PAR. LPS: 100 to 250 PAR. SPS: 200 to 450 PAR. Read PAR with a PAR meter (Apogee MQ-510 with a reef adapter, or a borrowed Seneye) at the coral's exact location, not at the water surface. PAR drops 30 to 60 percent from surface to substrate depending on light and water depth.
How often should I feed corals?+
LPS like hammer, frogspawn, and acan benefit from 1 to 2 spot feedings per week with mysis or reef roids. SPS take in light and dissolved nutrients more than direct feeding, but a weekly broadcast feeding of amino acids or coral foods boosts coloration. Soft corals (zoanthids, mushrooms, leather) rarely need targeted feeding and consume dissolved organics.
Why are my SPS coral tips turning white?+
Tissue recession from the base or tips signals one of three issues: alkalinity swing greater than 0.5 dKH in 24 hours, sudden temperature shift, or insufficient flow causing detritus settling on coral. The fix order: check alkalinity stability over 7 days, verify temperature swing under 1 degree, and increase flow on the affected coral. STN (slow tissue necrosis) reverses with 14 to 21 days of stable parameters.
Is dipping new corals really necessary?+
Yes, every time. New corals carry flatworms, red bugs, montipora eating nudibranchs, and aiptasia spores that wreck established reefs. Use a 10 minute Coral RX or Bayer dip, swish to remove pests, rinse in clean saltwater, then place in the display. The 15 minutes of dipping prevents months of pest treatment later.
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Priya Sharma
Priya Sharma writes for The Tested Hub.