However I'm a firm believer that this results in weak fish, doing all that but keeping the water at 25C or lower resualts in better fish but take longer to grow, and as i used to show fish i was looking for quality fish.
Fish are cold blooded so the warmer the water the faster they grow.
Thats the bases.
Warm water = faster growth, but shorter life span and weaker fish in general.
Cooler water = Slower growth rate, but longer lived fish and generally stronger.