+1 on the silcone....remove the sump like suggested run carbon and do water changes....by the sounds of it you corals should come back if you do all the above....for the most part the only silicone i would use would be the stuff you get from tank builders!

the stuff from rona and homedepot and what not are hit and miss

maybe get a HoB filter like Aquaclear and run it too help get the bigger stuff out till your skimmer is back up and running

Did you get the sump off line.

somehow you got bad silicone or there was something used to clean the glass that was still on it when you started using the sump - after the repair.

you need to get that sump out of there, tear it appart, clean the glass and rebuilt it using the right silicone, also let it dry before you install it, do some water changes and hope your tank makes it - run carbon.

You could take a hit and just sell off the corals AS IS at a loss....

When you are done building the sump again, use the left over water from a water change (healthy tank water) and buy a $5 chromis and put him and the old water from a change in the new sump to see if he gets sick or not. Better to do that than loose everything again.

Hi everyone!

Thanks for all the advice. We took the advice and the tank seems much happier/healthier. Corals might be a lost cause... Going to hope for the best but the fish and crabs are doing well.

Thanks again! So nice to get help when needed!

Silicone
 

I'd say silicone. Redo. Find silicone at an lfs.