💬 Free · 46 real questions
The questions reef keepers actually ask — gathered from real saltwater communities and answered the Coralkin way: calm, honest, water-first, and always with a clear "here's what to check." Search it, or jump to a topic.
Honestly, it's more about patience and consistency than difficulty. The hobby has a reputation for being impossibly hard, but the core skill is simple: keep the water stable and test it instead of guessing. Start with a fish-only or soft-coral tank, get the routine down, then grow into a reef — you belong here from your first clownfish.
It can be, but it doesn't have to start that way. The real costs are strong lighting, flow and testing — the things corals demand. A fish-only-with-live-rock or soft-coral nano can be started modestly; the expense scales with how demanding your livestock is. Buy the biggest tank you can comfortably house rather than upgrading twice.
The essentials: a tank, RODI water, marine salt, a heater, flow (a powerhead), live rock, and a test kit — plus reef lighting only if you'll keep corals. Mix and age the saltwater to the right salinity, add the rock, and cycle the tank before any livestock goes in. Get those basics stable and the rest is routine.
FOWLR (fish-only-with-live-rock) skips corals, so it needs no special lighting and tolerates a wider parameter range — the easiest way in. A reef tank adds corals, which need stable alkalinity, calcium and magnesium plus proper light and flow. Many keepers start FOWLR and convert to a reef once the routine is second nature.
A captive-bred ocellaris clownfish is the classic hardy first fish — alongside peaceful gobies, cardinals and a royal gramma. Choose captive-bred where you can (hardier, and no wild impact), and match the fish to your tank size. Browse the beginner-friendly options before you buy.
Bigger is more forgiving — a larger volume dilutes mistakes and holds salinity and temperature steadier, which is exactly what a beginner needs. A 20–40 gallon reef is a sweet spot; true nanos swing fast and are harder, not easier. Plan around your fish's adult size, not the little one in the bag.
The reef-standard targets: salinity ~35 ppt (SG 1.026), temperature 75–82°F, pH 8.1–8.4, alkalinity 8–11 dKH, calcium 400–450 ppm, magnesium 1300–1400 ppm, and nitrate and phosphate low but NOT zero. Ammonia and nitrite should read zero. See the full cited chart for every range and what to do when one drifts.
Aim for 35 ppt — specific gravity 1.026 at 77°F, the same as natural seawater. Fish-only tanks can sit a touch lower, but corals and inverts want full reef salinity. Measure with a refractometer (not a swing-arm hydrometer), and remember specific gravity changes with temperature.
A common routine is 10–20% weekly or every couple of weeks, adjusted to your nitrate and phosphate readings. Always mix and age the new saltwater to the right salinity and temperature first — never pour unmixed salt into the tank. Consistent small changes beat occasional big ones.
Only once your corals use those elements faster than water changes can replace them — a lightly-stocked or soft-coral tank often doesn't need dosing at all. Test first; if alkalinity or calcium drifts down between water changes, then dose to hold them stable. Never dose blind.
High nutrients feed nuisance algae, so bring them down with water changes and feeding control. But zero is the opposite problem: corals need some nutrients, and stripping the water bare invites dinoflagellates and pale, starving corals. Aim low-but-not-zero — nitrate roughly 2–15 ppm, phosphate ~0.03–0.10 ppm.
Because corals adapt to a stable value but are hurt by swings. A steady alkalinity of 8.5 dKH beats one bouncing between 7 and 11 chasing "perfect." Pick sensible targets, then change things slowly — small, gradual corrections, never big jumps.
Add an ammonia source (bottled ammonia, or let live rock do it) and let the bacteria build until the tank turns a dose of ammonia into zero ammonia and zero nitrite within 24 hours, with nitrate appearing. Test, don't guess — and add no livestock until it's done. Live rock or seeded media speeds it up.
Usually 2–6 weeks. The calendar doesn't decide it — the water does: it's cycled when a dose of ammonia clears to zero ammonia and zero nitrite within a day, and you're reading nitrate. Seeding with mature live rock or filter media can shorten it considerably.
Please don't. Fish-in cycling is stressful and often fatal, and damsels are aggressive and notoriously hard to catch out later once your rock is aquascaped. Cycle fishless with an ammonia source — it's kinder, easier, and lets you build the tank properly first.
A young tank goes through blooms of diatoms (brown dust) and other algae as it matures and finds its balance — it's normal and temporary, not a failure. Ride it out with patience, good flow and light nutrient control rather than nuking it. A cleanup crew helps once the tank is a little more settled.
Add a hardy fish or two only after the cycle finishes and parameters are stable, then stock slowly. Corals come later, once the tank has matured over weeks to months — start with soft corals and easy LPS, and leave SPS until the tank is well-established.
On most reefs a skimmer earns its place by exporting waste before it breaks down, which helps keep nutrients in check. But it isn't strictly mandatory — lightly-stocked and nano tanks can run skimmerless on disciplined water changes. It's a very helpful tool, not a law.
Use RODI (reverse-osmosis / deionised) water. Tap water carries nitrate, phosphate, silicates and sometimes copper or metals that feed algae and harm inverts — exactly what you're trying to avoid. Mix your salt with RODI, or buy RODI saltwater ready-made.
It depends on the coral. Soft corals and most LPS are happy under modest reef light (~50–150 PAR); SPS need strong, high-quality light (~200–400 PAR). Match the fixture to what you plan to keep, and acclimate corals to new light slowly to avoid bleaching.
Enough to keep detritus from settling and to sway the corals, without blasting them. Soft corals and LPS want gentle-to-moderate flow; SPS want strong, turbulent, random flow. Aim powerheads to bounce off the glass rather than jetting one spot.
No, but it helps. A sump adds water volume (more stability), hides equipment, and gives you room for a skimmer and refugium. Plenty of successful reefs — especially nanos — run without one.
At minimum: salinity, and for a reef, alkalinity, calcium, magnesium, nitrate and phosphate; plus ammonia and nitrite while cycling. A good liquid test kit (and a refractometer for salinity) beats guessing from clear water — the numbers are the only honest read on your tank.
There's no honest inch-per-gallon rule for marine — it comes down to each fish's minimum tank, adult size, swimming room and your filtration. Under-stocking is far safer for a beginner. Plan the whole stock list up front instead of buying on impulse.
Peaceful reef fish mix well; the classic clashes are two tangs (keep one per tank), mixing clownfish species, and two dwarf angels. Add the pushier fish last, and give everyone rockwork to break up sightlines. Check any combination before you buy, not after.
No. Captive-bred clownfish thrive without one and often never host — an anemone is an advanced animal that needs a mature tank and strong light, not part of a clownfish starter kit. Enjoy your clown first; consider an anemone much later, if at all.
No — clownfish are marine (saltwater) fish and cannot live in freshwater. The mix-up comes from how common they are in the trade and on screen. They need a cycled saltwater tank at reef salinity.
Big. Tangs are active grazers that need real open swimming length — commonly 90–125+ gallons depending on the species, not a nano. Swimming room is a welfare need, not a luxury, and most tangs are ich-prone, so quarantine matters just as much.
Keep one clownfish, or a single bonded pair of the SAME species — never two different clown species, which fight over territory. A pair naturally sorts into a larger female and a smaller male; add them together, ideally as juveniles.
Least aggressive first, most aggressive last, so no one gets to "own" the whole tank before the calmer fish settle in. Add a few at a time, never all at once, and quarantine each batch. The stocking checker flags the aggression order for your list.
Start with soft corals — zoanthids, mushrooms, green star polyp — and easy LPS like duncan and candy cane. They forgive modest light and flow and don't demand heavy dosing. Leave SPS (acropora, montipora) until the tank is mature and your parameters are rock-steady.
By type: acans and blastomussa want it low (~25–100 PAR), most softies and LPS moderate (~50–150), and SPS high (~200–400). PAR varies with your fixture and the coral's height, so borrow a PAR meter if you can — and always acclimate to brighter light slowly.
Usually light, flow, or water chemistry — the three to check first. Browning often means too little light or too-high nutrients; a coral that won't open may be getting too much flow or light, or sitting in unstable parameters. Rule out pests and a recent move, and change one thing at a time.
It's the reef difficulty ladder. Soft corals (zoas, leathers) are the forgiving beginners; LPS (hammer, torch, acan) are fleshy, feedable, and need stable alkalinity and calcium; SPS (acropora, montipora) demand high light, strong flow and pristine, rock-stable chemistry. Climb it in that order.
Temperature- and drip-acclimate it, inspect (and ideally dip) it for pests, then place it low and shaded at first. Raise it toward its target light over two to four weeks — more corals are lost to too much light too fast than to too little.
Euphyllia — hammer, torch and frogspawn — have long sweeper tentacles and want about 6 inches of clearance from other corals; torch stings even other Euphyllia. Acans, plate corals and leathers (chemically) also need room. Plan your spacing before you glue anything down.
Grazers help — certain tangs, turbo and trochus snails, and a tuxedo urchin will mow it — but a cleanup crew can't out-eat an underlying nutrient problem. Cut the fuel (nitrate and phosphate) with water changes and feeding control, and let the grazers keep the tidied rock clean.
An emerald crab is the usual pick — but be honest about it: it eats bubble algae mainly when hungry and can turn to corals or snails when it isn't, so keep it lean and remove big bubbles by hand (without popping them in the tank). It's a help, not a guarantee.
Peppermint shrimp (the real Lysmata wurdemanni) will eat Aiptasia — but identification matters, they may ignore it if well-fed, and look-alike species won't touch it. For reliable control, spot-treat the anemones with a dedicated product. Don't scrape them off, which just spreads them.
Algae is a symptom of nutrients plus light in an immature tank. A new tank's "ugly stage" passes on its own; a persistent bloom means excess nitrate/phosphate (overfeeding, tap water, loose stocking) or too long a photoperiod. Fix the husbandry first — a bigger cleanup crew alone won't do it.
Right-size it to your tank — a mix of grazing snails, a few scavengers, and maybe a hermit or two. Overstocking a crew just starves it, so start small and add as needed. Match the crew to your tank's real problems, not a snail-per-gallon myth.
That red, purple or brown slimy film is cyanobacteria — a bacteria, not a true algae — and it blooms where nutrients are high and flow is low. Improve flow, tidy up detritus, and bring nutrients into range; it usually recedes as the tank matures and balances.
Yes — it's the single best way to keep diseases like ich and velvet out of your display, and it's non-negotiable for ich-magnets like tangs. Keep new fish in a separate, cycled tank for a few weeks to observe and treat before they join the reef. Even a basic quarantine beats none.
That salt-grain look is most likely marine ich, usually triggered by stress or a parameter or temperature swing. Move affected fish to a quarantine tank and treat properly there — many reef-safe animals can't tolerate the medications. This is general guidance, not a diagnosis; for a serious case, get an experienced reefer's or aquatic vet's eyes on it.
Usually a swing or a shock: a big parameter change, an overdose, an equipment failure (heater or return pump), overstocking, or a dead animal fouling the water. The defences are the same as good keeping — stability, not overstocking, and testing so you catch trouble early.
Watch for a change from its normal self: clamped fins, rapid breathing, flashing (scraping on rock), hiding, or not eating. The first check is always the water — test it — because most "illness" in a new tank is really water quality. Quarantine anything visibly sick and treat it away from the display.
Short answers from the Coralkin team — kind, general guidance, not a diagnosis. When something looks wrong, test your water first, and for a serious case ask an experienced reefer or an aquatic vet. Deeper detail lives in each care guide and free tool.
