Note 2 - Significant Accounting Policies - Revenue By Product (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Net sales	$ 6,172	$ 5,582	$ 17,915	$ 17,101
Packaged Astaxanthin [Member]
Net sales	3,532	3,691	9,911	10,195
Packaged Spirulina [Member]
Net sales	1,382	1,277	3,899	4,447
Packaged Products [Member]
Net sales	4,914	4,968	13,810	14,642
Bulk Astaxanthin [Member]
Net sales	561	261	1,968	1,168
Bulk Spirulina [Member]
Net sales	496	312	1,548	1,033
Bulk Products [Member]
Net sales	1,057	573	3,516	2,201
Contract Extraction and R&D Services [Member]
Net sales	$ 201	$ 41	$ 589	$ 258