Opae Ula (Halocaridina rubra) are the closest thing the aquarium world has to a truly "set it and forget it" pet. No filter, no heater, no daily feeding — just a small brackish jar and a bit of patience. This guide walks you through setting up your first Opae Ula tank from empty jar to thriving micro-ecosystem.
What You'll Need
Before you start, gather a glass container (a sealed jar or open bowl both work), marine salt mix, dechlorinated fresh water, a thin layer of substrate, some porous rock or coral for surface area, and your shrimp. If you'd rather skip the setup entirely, our ready-made self-sustaining ecospheres arrive pre-balanced and ready to enjoy.
Step 1: Mix Your Brackish Water
Opae Ula are brackish-water shrimp, not freshwater. Aim for a specific gravity of roughly 1.010–1.015 using a marine salt mix and dechlorinated water. Mix it in a separate container, let it dissolve fully, and confirm the reading with a hydrometer or refractometer before it goes in the tank. Getting salinity right is the single most important step.
Step 2: Add Substrate and Hardscape
A thin substrate layer plus porous coral, lava rock, or fossil rock gives beneficial algae and biofilm somewhere to colonize. This hardscape isn't just decoration — it's the natural food factory that makes a low-maintenance tank possible. Coral also helps buffer the water and keep conditions stable.
Step 3: Establish Algae and Biofilm
Opae Ula graze constantly on naturally occurring algae and biofilm. Give your tank a few weeks of indirect light to let this food source develop. You can jump-start it by seeding the tank with live Chaeto algae, which provides both grazing surface and a bit of natural filtration.
Step 4: Add Your Opae Ula
Once the water is stable and some algae has developed, acclimate your shrimp slowly by floating the bag and adding small amounts of tank water over 30–60 minutes. Starting your first tank? A 10-pack of Opae Ula is perfect. For a fuller, more active display, step up to a 25-pack or 50-pack.
Ongoing Care
This is the easy part. Top off evaporated water with fresh dechlorinated water (never salt water — the salt doesn't evaporate) to keep salinity stable. Feed only a tiny pinch of food every week or two, and keep the jar out of direct sunlight. That's genuinely it.
Common Beginner Mistakes to Avoid
The biggest early mistakes are overfeeding, topping off with salt water instead of fresh, placing the jar in direct sun, and disturbing the tank too often. For a deeper dive, read our guide on the 9 Opae Ula care mistakes beginners make.
Frequently Asked Questions
Do Opae Ula need a filter or heater? No. They thrive at room temperature with no equipment, which is what makes them so beginner-friendly.
How long do Opae Ula live? With stable conditions, 10–20+ years is commonly reported — exceptional for any shrimp.
Can I keep them in a sealed jar? Yes. A closed jar can become a self-sustaining ecosystem that runs for years with almost no input.
How many should I start with? Ten is a great starting point. More shrimp means a livelier display and a better chance of breeding over time.
Ready to start your own little Hawaiian ecosystem? Shop all Opae Ula and ecospheres →