Don't just pop seeds in as the nute salts from the end of harvest will have been at a high level for bud production and the roots could mold and rot giving a none too friendly environment for your young seedlings.
sift through the coco and get as much root out as possible, flush though with water a few times and then use a product like Cannazyme which will deal with any left over root particles!
Cannazyme will also convert any Nitrites in to usable Nitrates
I love coco, it is a great hydro substrate and I would recommend it to anyone!
I personally can't be bothered to reuse coco as coco is not expensive and at my house it ends up going into the garden soil where is rots down and helps aerates the soil in the meantime!
I used to be a canna pro user but now I'm using Coco coinz from coco guru and they are great and come compressed in to little coins 10 coinz makes ! liter.
I also add Growstones (recycled glass) instead of perlite for extra airyness. Growstones GS-2 hold 30 time the air that perlite does!
I hope that helps.