It really depends on the "kelp pellets", and what they consist of. Most fish in the wild that consume large amounts of aquatic vegetation take in most of their protein/lipids from aquatic organisms that live within the algae. The following is an old quote from Ad Konings, regarding the herbivorous mbuna species found in Lake Malawi.
"although algae dominates the stomach contents of the majority of Mbuna, and they are considered herbivores, the foods that really make them grow are micro-organisms, insect nymphs & larvae, crustaceans, mites, snails, and zoo plankton, not vegetable materials at all.
And what Konings stated many years back is true, so simply feeding a fish in captivity a diet high in kelp, isn't going to be supplying it the type of nutrition that it would experience in the wild. In the wild most herbivorous species graze from sun up to sun down, which is not typically how they are fed in an aquarium, which is once or twice a day. So in captivity we need to supply a more well rounded, and more nutrient dense feed.
A study that was performed in 2001 by Dr. Ruth Francis-Floyd, Chris Tilghman, and RuthEllen Klinger from the University of Florida, shows just how important nutrient levels can be to certain species of fish kept in captivity. This particular study involved captive nutritional management of herbivorous reef fish using Surgeonfish as test subjects and were divided into 3 groups. The first Group was fed washed seaweed (ulva spp.). The second group was fed a commercially prepared all purpose type pellet food, and the third group was fed a commercial flake food that was supposedly designed specifically for herbivores.
At the end of the study, the ulva and flake fed groups suffered high mortality rates, (61%, and 39%), with the surviving fish showing clinical signs of malnourishment. Some had become emaciated to paper-thin condition. The second group (fed commercial pellets) performed the best, all fish gained steady weight, no deaths, and no apparent signs of any disease. The information from this study was made available during a lecture in 2001 at the Marine Ornamentals International Conference, held in Lake Buena Vista, Florida, and has also been published in "Marine Ornamental Species - Collection, Culture, and Conservation by James C. Cato, and Christopher L. Brown.
The seaweed diet - 39% of the test group exhibited extreme wasting, with 61% dieing before the end of the study.
The flake diet - Most fish gained weight, yet 27% came down with Hole in the Head/Head & Lateral Line Erosion Syndrome, 16% exhibited exopthalmia, corneal opacity, and apparent blindness, and 39% died before the end of the study.
The pellet diet - On average all of the pellet eating fish steadily gained weight, with no noticeable signs of disease, and no deaths.
Several years back I spoke with one of the professors involved in that study and while due to the politics involved she wouldn't go on record with regards to the commercial foods used, the pellet food used is the same pellet food that I currently feed my fish, all of my fish, including those classifed as herbivores. (NLS)
NLS or what I now feed Northfin both giving my fish exactly what they need I would never use any other brands
