Hole in the head

[RD]

Although tangs like non veggie food from time to time all tangs except the blue tang need algae to live and grow

Correct, but that does not equate to any tang requiring spirulina as the main part of its daily nutrient intake.

The optimum nutrient intake for tangs is far more complex than simply feeding them aquatic based plant matter in large amounts. Furthermore the premium pelleted diet known not to induce HLLE that was mentioned in the article on HLLE that was linked to above, was NLS, as was the pellet food used in the study by Tilghman, et-al that took place almost a decade ago.