Velvet (Amyloodinium) infections in fish can easily be avoided.

“5. Conclusions

Our results indicate that infestations of […] the gill parasite A. ocellatum can be avoided if a defined pattern of water quality is kept within production ponds with a defined fish stocking level. This pattern of water quality can be achieved by water renewal with night tides, which should be carried out by considering the dissolved oxygen values in production ponds.”

What?

Velvet can be avoided. 
It is not inevitable. 
Even in a scenario where it’s commonplace.

How?

Stocking levels matter.
Water quality (not our definition*) matters.

This is something I (and others) have been stating for years — mostly against stiff opposition in social media forums.  (Folks who generally see infections as inevitable and chemical treatments as mandatory….which they are if you don’t know or heed this info.)

The reciprocal interaction between degradation of glucose and ecosystem structure. Studies in mixed chemostat cultures of marine bacteria, algae, and bacterivorous nanoflagellates

Bacteria vs algae is the magic scenario we hope for when we carbon dose our tanks – that bacteria will “automagically” make the algae go away.  We see here that in some cases it does work out.  But as we see next, a “balanced system” promotes all three lifeforms.