Gertrudae Rainbowfish Care Guide
The Gertrudae rainbowfish (Pseudomugil gertrudae), often called the spotted blue-eye, is a tiny, peaceful gem that brings shimmering color and constant gentle activity to nano and planted aquariums. Despite the rainbowfish name, blue-eyes stay much smaller than their larger Melanotaenia cousins, which makes them ideal for smaller setups where a school of bold movement and finnage display really shines. This guide covers tank setup, water conditions, diet, temperament, and tankmates so you can keep these little fish thriving.
Gertrudae Rainbowfish at a Glance
Gertrudae blue-eyes are micro-fish, typically reaching only around an inch or so in length. The males show off spotted fins and flick their fins at one another in harmless displays, especially when kept in a proper group. They are active but peaceful, spending most of their time in the upper and middle levels of the tank. Because they are so small and gentle, they are best appreciated in a species-focused or carefully chosen nano community rather than a tank full of larger, boisterous fish.
Tank Setup
A heavily planted aquarium suits Gertrudae rainbowfish perfectly. They feel most secure with plenty of plant cover, fine-leaved plants, and some open swimming space near the surface. A small group can be kept in a nano tank, though giving them a bit more room always allows for a larger, more confident school and more natural behavior. Floating plants and a gentle filter flow help recreate the calm, vegetated waters they come from. For planting ideas, see our guide to easy beginner aquarium plants, and if you are choosing a smaller tank, our roundup of good fish for a 10-gallon tank and nano fish that stay small are helpful.
Water Conditions
Stability matters more than chasing exact numbers. Gertrudae blue-eyes do well in warm, gently acidic to neutral water within typical tropical community ranges, and they appreciate clean, mature water rather than a freshly set-up tank. Always add them to an established, fully cycled aquarium so the biological filter can handle their waste. If you are new to cycling, our walkthrough on how to cycle a new aquarium explains the nitrogen cycle step by step. Keep up with regular partial water changes to maintain pristine conditions.
Diet and Feeding
These tiny fish have correspondingly tiny mouths, so food size is the key consideration. Offer micro-sized dry foods, crushed flakes, and small live or frozen foods such as baby brine shrimp, microworms, and daphnia. A varied diet brings out their best color and condition, and small, frequent feedings suit their fast metabolism better than one large meal. For more on choosing community-friendly foods, see our guide to the best fish food for community tanks.
Temperament and Tankmates
Gertrudae rainbowfish are peaceful and a little shy, so they do best with calm, similarly sized companions and should never be housed with fish large enough to view them as a snack. Keep them in a group of at least six or more, as this encourages natural schooling, brings out male fin displays, and helps them feel secure. Good companions include other nano fish, small peaceful schoolers, and gentle invertebrates like Neocaridina shrimp. If you love the rainbowfish family, you may also enjoy our care guides for the threadfin rainbowfish, the Boesemani rainbowfish, and the turquoise rainbowfish, plus our general rainbowfish care guide.
Find Nano Rainbowfish in Cheyenne
At Tropical Treasures Wyo in Cheyenne, we quarantine and monitor all of our fish before they go up for sale, so you can stock your nano tank with healthy, well-acclimated stock. Stop by to see our selection of small schooling fish, plants, and shrimp, and chat with our team about building a peaceful nano community. We also offer free water testing to help you keep conditions stable for sensitive little fish like the Gertrudae blue-eye.