Adding on to cycled system

[Dan Bartlett]

When you add on to a cycled system, will there be nitrite and nitrate spikes as when you were going throught he cycling? 

[Leo White Bear]

Yes, there will be spikes of nitrites and possably ammonia until the new bed cycles.  Upside is that it doesn't take as long for the new GB to cycle as you are innoculating it with the bacteria from the FT and the old grow bed.  All I can say is let it spike, keep an eye on it and use the exact same media if that is the way your system is set up (Flood and drain media beds).

WB

[Dan Bartlett]

Thanks for the info Leo.

[TCLynx]

It really depends on how you go about adding onto the system.  If you were to add on more grow beds and then let them be a part of the system for a time before you add more fish, you may not experience any spikes.  If you go adding more fish and fish tank to a system that was already about at it's filtration limit at the same time as you add a brand new bed, you may well experience some spikes while the new bed cycles up.

If when you do the add on, you go disrupting the existing bacteria colony badly (say adding large amounts of chlorinated water or cause extreme fast pH swings or let the existing beds dry out for several days killing the bacteria during construction) you could also experience some bad spikes.