Why dosing matters in tanks with LPS corals
LPS corals, or Large Polyp Stony corals, build a hard calcium carbonate skeleton while displaying fleshy polyps that can react quickly to changes in water chemistry. That combination makes dosing especially important. If alkalinity, calcium, and magnesium drift too far or swing too fast, many lps corals respond with poor inflation, reduced feeding response, tissue recession, or slow skeletal growth.
Compared with some soft corals, lps corals usually place a steadier demand on major ions as they grow. Euphyllia, Acanthastrea, Micromussa, Favia, Blastomussa, Lobophyllia, and Scolymia all benefit from stable parameters more than from chasing elevated numbers. In most successful LPS systems, the goal is not maximum dosing, but predictable dosing that keeps alkalinity and calcium within a narrow range day after day.
Two-part dosing and kalkwasser are the most common methods for maintaining this stability. Two-part gives precise control over alkalinity and calcium independently, while kalkwasser can support both while also helping maintain pH. Using a tracking system such as My Reef Log makes it much easier to spot consumption trends before your corals show stress.
Dosing schedule for LPS corals tanks
The best dosing schedule for lps-corals tanks depends on coral density, calcification rate, and overall nutrient level, but consistency matters more than complexity. For most mixed or LPS-dominant aquariums, these are practical starting targets:
- Alkalinity - 8.0 to 9.0 dKH
- Calcium - 400 to 450 ppm
- Magnesium - 1250 to 1400 ppm
- pH - 8.1 to 8.4
- Salinity - 1.025 to 1.026 SG
If your tank is lightly stocked with lps corals, manual daily dosing may be enough. In a more mature reef with several growing colonies, splitting the daily dose into multiple smaller additions is usually better. This reduces parameter swings and keeps fleshy LPS tissue from dealing with abrupt chemistry changes.
Recommended frequency
- Test alkalinity daily for 5 to 7 days when starting a new dosing routine
- Test calcium 2 to 3 times per week until consumption is predictable
- Test magnesium weekly, then every 2 to 4 weeks once stable
- Dose two-part daily, ideally in 2 to 24 smaller increments with a doser
- Dose kalkwasser slowly through top-off, preferably spread across the full day or night cycle
Best timing for dosing
For two-part dosing, avoid adding the full amount at once. Alkalinity solutions can temporarily spike local pH and irritate coral tissue if dumped into low-flow areas. Add alkalinity in a high-flow sump section or overflow chamber, and separate calcium dosing by at least 5 to 10 minutes to prevent precipitation.
For kalkwasser, many reef keepers prefer nighttime dosing because pH naturally falls after lights out. Slow addition can help offset that drop. If you are also trying to improve pH stability, the strategies discussed in pH Levels for Zoanthids | Myreeflog are also useful for LPS systems because the same gas exchange and indoor CO2 principles apply.
Special considerations for dosing in LPS coral systems
LPS corals are not all identical in how they consume alkalinity and calcium. Fast-growing branching Euphyllia and encrusting Favias often increase demand more noticeably than slower, fleshy showpieces like scolys or open brains. A tank with several heads of hammer coral may consume more alkalinity than you expect, even if the total coral count seems low.
Another factor is nutrient level. LPS corals often perform well with moderate nutrients rather than ultra-low nutrient conditions. As a broad target, nitrate around 5 to 15 ppm and phosphate around 0.03 to 0.10 ppm often support healthy color and feeding response. If nutrients are stripped too low while alkalinity is pushed high, some lps corals can show burnt tips, receding edges, or reduced extension. Nutrient stability matters alongside dosing stability. While fish-focused, the broader relationship between feeding and nutrient management is also touched on in Nitrate Levels for Wrasses | Myreeflog.
Two-part vs kalkwasser for LPS tanks
Two-part dosing is usually the easiest choice when you want direct control. It works well for tanks with moderate to high calcification demand and allows easy fine tuning if alkalinity and calcium are being consumed at slightly different rates.
Kalkwasser dosing is excellent for low to moderate demand systems and can be very effective in LPS aquariums where pH runs low. Saturated kalkwasser typically contains about 2 teaspoons of calcium hydroxide per gallon of fresh water, but many hobbyists start at half strength to assess tolerance and evaporation rate. Because kalk adds alkalinity and calcium in a fixed ratio, it works best when your tank consumes them in roughly balanced amounts.
In higher demand systems, kalkwasser alone may not keep up, especially as colonies mature. In that case, a hybrid approach can work well - kalkwasser through ATO for baseline support, plus small two-part additions to close the gap.
Step-by-step dosing guide for LPS corals
1. Measure your baseline consumption
Test alkalinity at the same time each day for 3 to 5 days without changing your normal water change routine. If alkalinity drops from 8.6 dKH to 8.0 dKH over 3 days, your tank is using about 0.2 dKH per day. Repeat the process for calcium if needed. This gives you a real dosing target rather than a guess.
2. Set a stable target, not an extreme one
For most lps corals, aim for:
- Alkalinity - 8.0 to 9.0 dKH
- Calcium - 420 to 440 ppm
- Magnesium - 1300 to 1380 ppm
There is rarely a benefit to keeping alkalinity at 10 to 11 dKH in an LPS tank unless the whole system is built around that range and remains stable. Stability is usually more important than the exact value.
3. Start low and increase gradually
If using two-part, begin with 50 to 75 percent of the calculated daily amount, then test again after 2 to 3 days. Adjust slowly. A safe correction rate for alkalinity is generally no more than 0.5 to 1.0 dKH per day. Rapid alkalinity jumps often stress fleshy corals.
If using kalkwasser, start with a weaker mix and monitor pH, alkalinity, and evaporation. Never add kalk slurry directly to the display. Dose only the clear solution and dose it slowly.
4. Place dosing output in high flow
Direct the dose into an area with strong water movement, away from coral tissue. LPS corals have large, delicate polyps that can be damaged if concentrated supplement contacts them directly. This is especially important for acans, scolys, and lobos placed lower in the tank.
5. Re-test and fine tune weekly
As lps corals grow, consumption changes. New frags may use little at first, then suddenly increase demand once established. Logging each test in My Reef Log helps reveal whether alkalinity is drifting downward over weeks, even when daily changes seem small.
6. Coordinate dosing with feeding and maintenance
LPS corals often benefit from target feeding once or twice per week, especially acans, blastos, and scolys. Increased feeding can boost growth, and faster growth often means increased dosing demand. After adding several new frags or after a fragging session, keep a closer eye on alkalinity for 1 to 2 weeks. If you are expanding your collection, Top Coral Fragging Ideas for Beginner Reefers is a useful companion resource.
What to watch for after dosing changes
LPS corals usually tell you fairly quickly whether your dosing approach is working. Watch both the numbers and the animals.
Signs your LPS corals are responding well
- Full, even polyp inflation during the normal photoperiod
- Good feeder tentacle extension at night or during feeding
- Steady skeletal growth at the base or edge
- Improved coloration without washed-out tissue
- Less random recession after parameter stability improves
Signs your dosing may be off
- Tissue recession at the base of Euphyllia or around the rim of fleshy LPS
- Sudden deflation after an alkalinity correction
- White precipitation on heaters, pumps, or sump walls
- Chronically low pH with weak calcification
- Alkalinity drifting despite regular dosing, often a sign the dose is too low
If you notice repeated precipitation, your alkalinity and calcium supplements may be interacting before they disperse, or magnesium may be low. If LPS tissue looks irritated right after dosing, improve dilution, increase spacing between parts, or reduce each individual dose size.
Common mistakes when dosing for LPS corals
Chasing numbers instead of stability
One of the biggest mistakes in dosing is reacting to every single test with a correction. Small day-to-day variation is normal. LPS corals usually prefer an alkalinity that stays at 8.3 dKH every day over one that bounces between 7.5 and 9.5 dKH.
Using kalkwasser without respecting evaporation limits
Kalk dosing is capped by how much fresh water your tank evaporates. If your system evaporates only 1 gallon per day, you cannot force more kalkwasser through the ATO without lowering salinity. In that case, switch to stronger supplementation with two-part or use a combined approach.
Ignoring magnesium
Many hobbyists focus on calcium and alkalinity, but magnesium helps keep the system chemically balanced. If magnesium falls under about 1200 ppm, it becomes harder to maintain calcium and alkalinity without precipitation.
Making large corrections too quickly
LPS corals tend to dislike abrupt parameter shifts. If alkalinity is low, raise it in measured steps over 1 to 3 days rather than fixing the full deficit at once. The same principle applies after a missed dosing day.
Dosing into the display near corals
Direct contact from concentrated additives can burn tissue. This is a common but avoidable coral task mistake. Always dose into a high-flow area away from coral flesh.
Failing to adjust as the tank matures
A dosing plan that worked with five small frags may be completely inadequate six months later. As colonies plate, branch, or encrust, consumption increases. Reviewing historical trends in My Reef Log can help you catch this before your lps corals show obvious stress.
Conclusion
Successful dosing for lps corals is about consistency, measured adjustments, and watching coral behavior as closely as test results. Whether you choose two-part dosing, kalkwasser, or a combination of both, keep alkalinity, calcium, and magnesium stable within sensible ranges and avoid sudden changes. LPS corals often reward that stability with fuller inflation, stronger feeding response, and steady skeletal growth.
As your reef evolves, revisit your schedule regularly. Coral growth, feeding, evaporation, and seasonal pH shifts can all change demand. With careful testing, patient adjustments, and organized records in My Reef Log, this coral task becomes far more predictable and much easier to manage long term.
Frequently asked questions
What alkalinity is best for LPS corals when dosing?
For most lps corals, 8.0 to 9.0 dKH is a strong target range. More important than the exact number is keeping it stable. Try to avoid daily swings larger than about 0.3 dKH.
Is kalkwasser enough for an LPS tank?
It can be enough for low to moderate demand systems, especially smaller tanks or tanks with fewer calcifying corals. In heavily stocked LPS aquariums, kalkwasser alone often falls short because evaporation limits how much you can add.
How often should I test when starting a new dosing routine?
Test alkalinity daily for at least 5 to 7 days, calcium 2 to 3 times per week, and magnesium weekly. Once the dose is stable, you can reduce frequency, but any major coral addition or growth spurt should trigger more testing.
Why do my LPS corals shrink after dosing?
Common causes include dosing too much at once, local contact with concentrated supplement, rapid alkalinity correction, or precipitation from poorly spaced two-part additions. Reduce dose size, improve flow at the dosing point, and separate alkalinity and calcium additions by several minutes.