When to put slatye in the tank.

When do I put slate or other alternative breeding sites in with my breeding size koi? I have a pair forming in there and need to know this.

You can add them at any time, not only are they breeding sites they can also use them for cover when being harassed. :D

:( Capree: Thanks I will put two in the tank tonight.

Now is as good as any other time. Throwing a spawning substrate is one of several stimuli for them to pair up if unpaired; if they're well conditioned, spawn - In my experience at least. I suspect that it might be a "cultural" thing in the same way that some killer whale "pods" solely hunt for other marine mamals while other "pods" hunt solely fish including white sharks. It doesn't harm to try it.