Gelatin binder in frozen fish foods

[RobertK]

Hi Randy,
I was just reading an article on cyanobacteria by Bob Fenner, and in it he said that frozen foods such as Formula 1 and 2 contain gelatin binders which release large amounts of DOCs that can fuel cyano growth. I do use these foods, and I've been fighting a battle with cyano for over a year now; I've made all kinds of improvements to the tank and the water quality seems pretty good, but I still have cyano on the sand in the front of the tank. Can you elaborate at all on the gelatin issue and whether or not you agree with his claims? I'll probably change foods but my fish love the stuff and I'd like to know if you think it makes sense to do so.
Thanks,
Robert

[Randy Holmes-Farley]

Gelatin is largely protein, and as such contains a substantial amount of nitrogen and possibly some phosphate. It could be used by organisms as is (gaining energy or amino acids from the protein) or indirectly after bacteria break it down into CO2, ammonia, and some phosphate.

It doesn't, however, take much gelatin to solidify a small cube. Look how little solids gels a whole tub of Jello, and how little nutritional value Jello provides.

I can't really say for sure where it might be a big factor in cyano or not. I use these gel cubes all of the time, but I do have a small but acceptable amount of cyano.

Let's just say I'm skeptical of it's importance relative to all of the other things that drive algae.

[RobertK]

Thanks, Randy
I'm a little skeptical myself, but I've tried everything else and still have cyano. I might try an uncontrolled experiment and leave the gelatin-containing foods out of my fishes' diet for a while to see if it makes a difference.

[Randy Holmes-Farley]

Robert:

Sure, no reason to not try it.

I agree with the general consensus that cyano seems to thrive in high organics. I had a cyano problem about 5 years ago and cured it with better skimming.