Midas Blenny

Color change is very common in Midas Blennies and usually reflects mood, environment, and hierarchy rather than disease. Bright yellow or golden: typically a relaxed, confident fish in good health. Darker, brownish/mottled: often seen when stressed, newly introduced, or when trying to blend with rockwork for security. Bluish or more subdued gold with a dark back: frequently seen in males displaying or when asserting territory. Sudden, blotchy paling with clamped fins, heavy breathing, or hiding can indicate acute stress or illness (check for aggression, water quality, and parasites). If the fish eats well, swims normally, and only shifts coloration with different situations (feeding, lights on/off, new tankmates), it is usually normal physiological color change.

Midas Blennies can become territorial, especially in smaller tanks or when they feel they “own” a specific cave. To manage aggression: 1) Upgrade or ensure at least ~40–50 gallons with plenty of rockwork and multiple caves so newcomers can avoid direct line of sight. 2) Rearrange rocks and decorations right before adding new fish to reset territories. 3) Add new, similarly sized or slightly larger tankmates rather than very timid, slender fish that resemble the blenny’s body shape (dartfish, firefish, some wrasses). 4) Feed small, frequent portions of varied foods to reduce food-guarding behavior. 5) Temporarily confine the Midas in an acclimation box inside the tank when introducing new fish; after a few days, release it so hierarchy re-establishes more gently. If severe aggression continues, long-term separation or rehoming might be needed.

That behavior is completely typical for this species. Unlike many bottom-perching blennies, Midas Blennies are midwater hoverers and spend a lot of time in open water, especially near their chosen bolt-hole. To keep it comfortable: provide at least one snug cave or crevice where it can retreat quickly, preferably near moderate flow (they enjoy hanging in currents). Use a tight-fitting lid or mesh top, as this open-water swimming style is associated with a higher risk of jumping when startled. A longer tank (more horizontal swimming room) is ideal. As long as it has a secure retreat and is eating, this midwater “anthias-like” swimming is expected and healthy.

Keeping more than one can work, but it requires planning and space. In small tanks, multiple Midas Blennies almost always fight. For groups, aim for a tank 4 feet or longer (75+ gallons) with heavy rockwork and multiple caves spread across the tank. Introduce them all at the same time as small, juvenile individuals from the same supplier when possible, which reduces territorial disputes. Avoid mixing obviously larger and smaller individuals to reduce bullying. Watch for one fish relentlessly chasing another; if one fish is forced to hide constantly, the group is not stable and the bullied fish should be removed. In many home tanks, a single specimen remains the most reliable option; groups are best attempted only by experienced keepers with large systems and the ability to separate individuals if needed.

Midas Blennies are active planktivores and burn a lot of energy, so they do best with small, frequent, high-quality feedings rather than a single large one. Aim for 2–3 feedings per day. Prioritize: 1) Frozen foods such as enriched brine shrimp, mysis shrimp, finely chopped marine mix, and copepod-based blends. 2) High-quality marine pellets or flakes with significant marine protein content (fish, krill, squid) rather than mostly terrestrial fillers. 3) Occasional additions of vitamin- and HUFA-enriched foods (e.g., foods soaked in Selcon or similar) to support color and immune health. They are not strict algae grazers like some blennies, so do not rely on film algae as a main food source. If its belly remains pinched despite good food variety, check for internal parasites (stringy white feces, progressive weight loss) and consider a medicated food regimen in a separate tank if indicated.