Starting a system: why you wait before adding fish

Students will

• Explain why fish added to a brand-new system can become stressed.
• Describe cycling: feeding the bacteria first, with no fish in the tank.
• Read a cycling chart: ammonia peaks first, then nitrite, then nitrate rises as both fall.
• Say how growers know a system is ready for fish.

New words

cycling

Growing the helpful bacteria in a new fish system before it is ready for fish.

Talk about it

What else has to be set up and ready before it can do its job? Think of a new team, a new garden, or a new school year.

Check questions and answers

1. Why do growers wait before adding fish to a new system?

   • The crew isn't ready, so ammonia would build up (answer) Right. With too few bacteria, ammonia builds up and stresses the fish.
   • The water is too cold for fish Not quite. Temperature matters, but the big wait is for the crew to grow.
   • The plants have to grow first Not quite. The fish aren't waiting for plants. The crew has to grow first.

2. How do growers know a new system is ready for fish?

   • Ammonia and nitrite test near none, and nitrate shows up (answer) Right. That means the Munchers and Finishers are both doing their jobs.
   • The water looks clear Not quite. Clear water can still hold ammonia. Only a test shows it.
   • Ammonia tests high Not quite. High ammonia means the Munchers are still behind.

3. About how long does cycling a new system take?

   • Several weeks (answer) Right. It often takes about a month, and longer in cold water.
   • About one hour Not quite. The crew grows slowly. An hour is far too short.
   • About two years Not quite. It takes weeks, not years.

Teacher note

This lesson needs no live fish; the simulation shows the wait on screen. If a class does keep fish, follow the school's animal policy, and an adult is in charge of their care.