Note 2 - Significant Accounting Policies - Revenue By Product (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Net sales	$ 7,504	$ 10,044	$ 23,265	$ 24,143
Packaged Astaxanthin [Member]
Net sales	4,513	6,012	13,870	15,388
Packaged Spirulina [Member]
Net sales	1,878	3,212	5,523	6,208
Packaged Products [Member]
Net sales	6,391	9,224	19,393	21,596
Bulk Astaxanthin [Member]
Net sales	377	229	879	823
Bulk Spirulina [Member]
Net sales	613	533	2,590	1,663
Bulk Products [Member]
Net sales	990	762	3,469	2,486
Contract Extraction [Member]
Net sales	$ 123	$ 58	$ 403	$ 61

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration