Freshwater cycling builds a single layer of nitrifying bacteria on filter media and substrate. The cycle is functionally complete in 4-8 weeks. Saltwater reef cycling is more complex because:
"Live rock" is rock that has been seeded with bacteria, microfauna, and sometimes coralline algae. Two sources:
Live rock cycles faster - 3-5 weeks typical - because the bacterial population is already present. The trade-off is paying for shipping wet rock (heavy) and accepting some pest risk.
"Dry rock" is rock that has been bleached, dried, or cured to remove all organic material. Sources:
Dry rock cycles slower (6-10 weeks) but starts pest-free, ships dry, and lets you aquascape on a workbench before filling the tank. Most modern reefkeepers prefer dry rock for control.
Use 80-90% dry rock plus 10-20% live rock as a "starter" piece. The live rock seeds bacteria and microfauna into the system; the dry rock provides the bulk of structure. Cycles in 5-7 weeks with low pest risk.
Three options to feed the bacteria:
Dose pure ammonia chloride to 2-4 ppm. Test daily. The cleanest approach. Combine with Dr Tim's bacterial seed product to accelerate.
Add Bio-Spira, Fritz Zyme 9, or Dr Tim's One & Only on day 1. Add a small amount of food daily for 14 days. The bacteria establish on existing organic matter (silts in dry rock, dead organisms in live rock).
Drop a piece of raw, uncooked shrimp into the tank on day 1. As it decomposes, it produces ammonia. Slower and smellier but free.
Ammonia rises rapidly from your dosing or shrimp source. May reach 4-8 ppm. Nitrite zero. Nitrate zero. Bacteria are establishing but population is small.
Ammonia begins falling as Nitrosomonas bacteria multiply. Nitrite spikes to 2-4 ppm or higher. This is the longest phase. Patience.
Both ammonia and nitrite return to zero within 24 hours of dosing. Nitrate accumulates (10-40 ppm typical). The biological filter is functional.
Now the hard part. Once the cycle completes, the tank goes through a "uglies" sequence:
The ugly stage subsides. Coralline algae appears (purple/pink crust on rocks - sign of stability). Pod populations explode. The tank starts looking like a reef.
Bacterial diversity continues expanding. Microfauna stabilizes. Parameters become predictable. Coral can be added gradually.
Once ammonia + nitrite zero for a full week, add a starter CUC: 5-10 turbo or trochus snails, 2-3 hermit crabs, 1-2 nassarius snails. They'll eat the diatom bloom.
One small hardy fish: a Royal Gramma, a captive-bred clownfish, a Yellow Watchman Goby. Quarantine first if you're not pre-quarantined. Feed sparingly. Watch parameters.
Zoanthids, mushrooms, leathers, branching hammer/frogspawn/torch, Acanthastrea, Goniopora. These tolerate the parameter swings of a still-maturing reef.
The tank has been stable enough for 3+ months. Begin adding SPS frags - start with hardier species like green slimer Acropora yongei, common millepora, Stylophora, Pocillopora. Save the LE pieces for month 9-12.
Now your SPS husbandry framework is mature. Pink Lemonade, Walt Disney Tenuis, ORA Pearlberry can be added with confidence.
The single biggest cause of new-tank crashes. The biofilter has finite capacity. Adding a tang to a 4-week-old tank overwhelms the bacteria, ammonia spikes, livestock dies.
Water changes during weeks 2-6 of cycling can disrupt the bacterial population. Resist the urge to "clean up" the diatom bloom with massive water changes. Wait it out.
Even captive-bred clownfish can carry parasites. The "first fish in" should still be quarantined. New tanks are especially vulnerable to disease introductions because there's no buffer.
Running full SPS-spectrum lighting on a brand-new tank produces hair algae blooms that take months to recover from. Run lights at 30-50% intensity for the first 3 months.
Some reefers run skimmers off during cycling under the theory that the bacteria need the organics. Modern thinking: run the skimmer from day 1. Bacteria establish on rock and substrate; the skimmer removes excess dissolved organics.
Take a cup of substrate, a piece of established live rock, or a sponge from a friend's mature reef. Cycle time can drop to 14-21 days. Trade-off: pest introduction risk.
Bottled bacteria + ammonia dosing can cycle a tank in 7-14 days under perfect conditions. Trade-off: bacterial population is fragile until secondary diversity establishes; aggressive stocking can crash quickly.
Established live rock from a vendor's curing system can drop cycle time to 7-14 days. Trade-off: cost ($8-12/lb vs $3-6 for dry).
Saltwater reef cycling is patience plus discipline. 6-10 weeks for ammonia/nitrite to zero. 3-6 months for visual stability. 9-12 months for true SPS-readiness. Skipping steps doesn't work; the bacteria don't accelerate because you're impatient.
The reefer who waits 12 months before adding their first $400 Pink Lemonade frag is the reefer who has it growing 18 months later. The reefer who adds a Yellow Tang on week 4 is the reefer who watches it die on week 5.