Biocube 29 - adding 30 gallon sump - Questions.

[Beezwax404]

So I have a 29 gallon biocube with multiple LPS and a mandarin. The mandarin was eating frozen food at the store but since I got him home he hasn't touched any frozen and I believe my pod popultation is decimated although I still see munnid isopods on the glass. So I freaked out and bought a sump. I got a deal on a 30 gallon sump and ordered a HOB overflow. My plan is to add a refugium and stock it with pods to hopefully feed the mandarin before its too late.

I need to know if adding this much extra water is going to shock my fish or corals? If I match the same parameters will that be sufficient? My nitrate hovers around 20so adding that much water will bring it to around 10. Will that be a shock?
Im just wanting to know if there is anything I should know other than just mixing up 30 gallons and hooking it up to my 29gallon tank?

Any help would be appreciated.

 

[scottedontknow]

How much rock? Marinepure?

 

[Beezwax404]

I have 20lb of live roxk in display but its super porous so it looks like alot more. No i dont have any marine pure. I gotta set up the sump tonight so i can start the refugium. I feel like my mandarin is starving.