Who Gives A Fish Forums

Always isolate if possible. Black band spreads fast, and you don't want it jumping to other SPS. I lost a whole Montipora capricornis colony last year from cross contamination. Use a separate frag tank if you've got one.

If the bucket test shows fluctuations, note the exact behavior—Eheim might ask for details. Also, ensure your tank's flow isn't creating cold spots near the heater. A powerhead can help distribute heat evenly.

Eheim Jagers are generally reliable, but thermostat failures aren't unheard of. First, verify the heater's fully submerged and the dial isn't obstructed. Second, test it in a bucket with a separate thermometer to confirm inconsistency. If it's faulty, contact Eheim—their customer service is decent.

Favia's a possibility