"Northfin sounds great along with them clearly stating they don't use harmful preservatives such as Ethoxyquin".
Here's a good analysis of foods
Northfin Fish Foods Ingredients Analysis
Northfin has "NO Ethoxyquin" and "FILLER FREE"."
Straight from the horses mouth. Below is their website:
"NorthFin Premium Fish Foods does not use any preservatives or harmful chemicals to preserve its product line.
"All of NorthFin’s Premium Product Line consist on formulas which are 100% Filler Free".