If you don't need a ton of coco, I'd go with what
@gwheels suggested and buy a bag of pre-expanded and buffered coco coir.
If you decide to go with 5kg bricks, just be aware that a thorough rinse is always a good practice with compressed coco, even if it claims to be washed. You wouldn't believe the amount of crap that will wash out. A tip for rinsing is to put the coco brick in a 10 gallon fabric pot and either set it in a bathtub or outside and run water through until it is expanded and the rinse water runs clear.
Then after rinsing it until the runoff water runs clear, it's a good idea to buffer it. The way I do it, and this isn't the only way, is to mix up some cal-mag and thoroughly soak the expanded coco. Coco coir likes to grab onto calcium, so by buffering it first you prevent the coco from stealing calcium from your nutrients and robbing it from your plants.