Read through this thread, there are some issues of concern.
First, your pH is 8.2, that is very high. I am wondering if this is due to the "sand" mentioned in your first post? It seems you bought live sand (sand with bacteria) which may have been intended for marine tanks, not freshwater. Or there is something in your tanks raising ph (the sand or rocks). What is the pH of your tap water on its own? This issue may have been part of the reason for your fish dying.
Second, after being without a source of ammonia for a couple of days you will be cycling from start, so no purpose in transferring media from the old filter now. Clean the filter, set it back up. The sand may have to go, depending upon the preceeding. Get one or two hardy fish but fish that you want to keep, as they will (hopefully) live on for many years.
You mentioned cichlids somewhere...what type? A 10g is small quarters for most cichlids, except maybe a single pair of dwarf apistogramma.