MY 20 some years in marine fish keeping (and joy) have led me into the following conclusions, which I'd like to share with those who's seeing his/her lovely fish getting discolored or have lateral line erosion and worse, hole in head, when your cherished fish only survived but not flourish in your tank.
1. Minimize stresses to fish. Use ground probe to discharge electric shock and use quieter pump to reduce tank noise. The fish in your tank will never get use to the noisy humming pump and electric shocks because they have not experienced any of these in their natural reef.
2. Use a powerful and yet low noise protein skimmer to remove stuff coming off from the other end of the fish and uneaten food. I'll get to the DIY skimmer design in a different discussion.
3. Use an algae scrubber to remove the remaining ( carbon dioxide, phosphate, nitrate). Nitrate concentration (up to 350ppm) is NO concern to most fish, however. The algae will also keep the correct pH for you.
4. Use water conditioning additives to promote growth of incidental (came in as guests with your fish) invertebrates. Worms, sponges would grow in your tank for your fish to pick on as desserts. Most salt
mixs on the market do not support invertebrate growth without additive. This is how my fish in my tank live long (Most >5 years, some >10 years) and without discoloration even though I practiced water change ONCE a year for the past 13 years.
5. Use pellet active carbon (not powder, 2lbs/100gal) to remove yellow coloration. Making sure no powdery carbon in the tank because powder carbon in water irritates the fish.
6. Use a good UV sterilizer (10w/100gal) to kill parasites. Change UV bulb annually.
7. Feed fish with dry pellets or flakes as staple food, which will keep them in shape but may not be able to maintain their bright color. Feed the fish with chopped shrimp, mussel, oyster or any other invertebrates once a week
or so as a supplement to the live invertebrates food naturally grown in your tank. Balance the feeding frequency between dry and wet food to control their body weight. I had two sad stories on overfed moorish idol and green trigger to share with later when I did not balance the dry-wet food correctly.
There are more details to come and this is just a beginning....Cheers!!