[DJRansome]

Try cutting your nitrates in half and see if growth improves.

 

[Smeagol]

My mbuna haven't grown as fast as I expected either. I've had them 14 months now. I'm not saying they haven't grown at all, just not as much as expected. I'm terrible at estimating sizes, but here goes:

• Acei range from a 1.75" runt to a 4.5" dominant male, while the rest are in the 2.5" to 3" range.
  
  
• Yellow labs range from a pair of 1.25" (born in my tank) to a pair of 3" females (but they were almost 3" when I got them). The rest are in the 1.75" to 2.25" range.
  
  
• Maingano are all about 2.75" except one runt who is only 1.75".

Do these sizes sound small to you, or do they sound normal? I do multiple water changes per week. My nitrates are never above 10. I feed once per day (in the evening).

 

[marten]

I'd be curious about how water hardness might affect growth rates too. As far as i know, it can affect their metabolic rate.