Factors affecting powerhead needs:
* Tank layout and shape: A long, narrow tank requires more powerheads to create good flow than a shorter, wider tank.
* Coral types: Some corals require stronger flow than others.
* Desired flow pattern: Do you want a strong, directed flow or a gentler, more random flow?
* Other equipment: A sump, protein skimmer, or other equipment can create additional flow, reducing the need for additional powerheads.
General guidelines:
* Flow rate: Aim for at least 10 times the tank volume in flow per hour. So, for a 75-gallon tank, you'd want at least 750 gallons of flow per hour.
* Powerhead placement: Position powerheads to create a varied flow pattern, avoiding dead spots.
* Multiple powerheads: Using multiple smaller powerheads is generally preferable to one large powerhead for better flow distribution.
Recommendations:
* Start with two: Two moderately sized powerheads are often a good starting point for a 75-gallon tank.
* Adjust based on needs: Monitor your tank and adjust the number and placement of powerheads as needed.
* Consider your corals: Research the flow requirements of your specific coral species and adjust accordingly.
* Consult with an experienced reef tank keeper: If you're unsure, seek advice from someone with experience.
Remember, it's better to err on the side of too much flow than too little. Adequate flow is essential for proper water circulation, nutrient distribution, and coral health.