Between weeks five and seven, the blades will start to reach the optimal outplant length of 2 mm. The golden color from the week prior will be replaced by a beautiful, dark brown, and the blades will be easily identifiable. It is okay to keep the spools in the hatchery for a little longer beyond the six to seven-week mark, but once the lengths of the blades start approaching 4 mm, the blades will quickly start to starve and lose color, taking up the tank’s nutrients much more quickly than you can replenish it.

It should be noted that spools in a flowthrough system can grow to a much bigger size before starving as long as the nutrient replenishment continues and the lights are dimmed lower. The exact tank conditions are noted on this Environmental Conditions chart.