Hydor MINI HEATER Aquarium Heater 7.5 Watts for Tanks 2-5 gal for $9.38

Safely increase the water temperature in your small glass or acrylic marine or tropical aquarium by a few degrees. The compact Hydor Mini Heater features a small, flat, space-saving design that lets it hide discreetly in small tanks and bowls. It’s completely submersible and safe to use if left running dry.