Blue Manna powder is basically an extract of Aphanizomenon flos-aquae. It contains concentration of phycocyanin and Phenylethylamine. It is the extract of Blue green Algae and is said to promote Greater mental energy and memory, Mental and emotional balance and also healthy joints and tissues.
On the other hand, Spriulina is a food supplement which is same as Aphanizomenon flos-aqu as it is also extracted from Blue Green Algae. Hence they are more or less the same.