Evidence rule
This addendum preserves weak claims when they are potentially useful, but labels them explicitly as agency summary, specialist observation, community experiment, breeder claim, hypothesis, or unresolved. A tolerance range is not converted into a breeding target.
Halocaridina rubra — lifespan and reproductive frequency
Hawaiʻi Division of Aquatic Resources currently states that ʻōpae ʻula can live over 20 years. The 2015 Hawaiʻi State Wildlife Action Plan summarizes captive lifespan as up to 20 years and states that they reproduce one to two times per year.
Those frequency numbers should not be treated as universal. A separate five-year laboratory study found reproduction throughout the year, with significant seasonal and genetic-lineage effects and the mixed-lineage colony being the most prolific. Aquapedia therefore stores “1–2 broods/year” as an agency summary, not as a fixed species maximum.
Halocaridina rubra — water chemistry interpretation
A documented West Hawaiʻi pool containing both H. rubra and M. lohena measured 12.5 ppt, 21.8 °C, and pH 7.50. Other natural pools span much broader salinity and chemistry. This is habitat evidence only; it does not establish a breeding optimum.
No controlled source found in this sweep establishes a single GH, KH, TDS, or pH optimum for reproduction. The strongest direct breeding variables remain salinity and temperature: 18–20 ppt / 23–25 °C for the Iwai breeding population, with 15 ppt / 24 °C also supporting long-term reproduction in research colonies.
Metabetaeus lohena — adult longevity
The 2015 Hawaiʻi State Wildlife Action Plan summarizes M. lohena lifespan as about six years. A long-running hobby keeper later reported individual Alpha Opae still alive at roughly seven years. The latter is retained as a community longevity observation, not a controlled lifespan estimate.
Metabetaeus lohena — larval bottleneck
The strongest official evidence remains the Hawaiʻi captive attempt summarized by U.S. Fish and Wildlife Service: larvae reached the fourth instar, developed a long defensive spike, and then died. The agency interprets this together with population genetics as evidence that an oceanic dispersal phase may be important. That is a scientific interpretation, not direct proof of a mandatory ocean phase.
Experienced keepers repeatedly report that getting adults berried is easier than rearing larvae. One forum breeder reported that moving larvae to about SG 1.018–1.020 kept them alive for roughly one week, but not through settlement. Other attempts using both brackish and full-seawater conditions also failed within days to about a week.
These observations suggest higher salinity may improve short-term survival, but they do not prove the correct salinity, transition schedule, or settlement salinity.
Cohabitation with regular ʻōpae ʻula — conflicting evidence
Fuku-Bonsai reported a mixed display in which adding four M. lohena caused H. rubra to abandon its protected breeding area and reproduction ceased in that tank. The observer suspected predation on larvae/postlarvae/juveniles but did not document a controlled experiment proving the mechanism.
However, another experienced keeper later documented berried H. rubra in a mixed tank with Alpha Opae, directly showing that coexistence does not always eliminate reproduction. That report does not prove there is no negative effect on larval survival, brood frequency, or recruitment.
Aquapedia status: CONFLICTING SPECIALIST/COMMUNITY OBSERVATIONS — context-dependent and unresolved. Alpha Opae remain a plausible predation/stress risk in breeding-focused colonies, but “Alphas stop Opae breeding” must not be presented as a universal rule.
Current unresolved Alpha protocol variables
Until one of these reaches repeatable juvenile settlement, Aquapedia should not publish a single “Alpha breeding recipe” as fact.
Public research references
Listed research leads are not automatically supporting evidence for every individual claim.
No eligible public supporting URLs are attached to this summary yet.