Overall water quality and fish health

Question
Karen & Readers,
Good morning from Kentucky.  I have a few questions that I would like to ask.  I have owned my fish tank for 6 years now.  All my fish are around 4-6 years old.  Lately I have had problems with cloudy water and ick on my oldest and largest fish.  Also, all 5 of my fish are goldfish that have grown to be fairly large for a 55 gallon tank, but they still have plenty of room to move around.  The tank has plenty of filtration.  I have two dual penguin power filters, a underground filter hooked up to a powerhead for maximum circulation.  I do a 40% water change every 2-3 weeks and replace the filters every two months.  I also use a Nitra-zorb to help out with nitrate.  I have no plants or ordainments in my tank so that my fish have more room to swim.  I use all premium products and my ph stays around a 7.0.  My ammonia is always at a 0.  Do you think I am keeping my tank too clean?  If so, what would you recommend that I change?  When it comes to ick, it always get to only one fish.  Do you know why it only effects my oldest fish?  Whenever I notice ick I do a 40% water change, add aquarium salt, use Nox-Ich and bump the heater up to around 77-79 degrees.  It usually kills the ick, but it leaves his fins badly damaged and by time his fins are back to normal the ick strikes again.  Could you please give me some advice on this.  Maybe I am doing something wrong and I would like to know.  I appreciate your time and expertise.
Thanks,
Andy

Answer
Hi Andy,
Sounds like you have done an excellent job with your goldfish.The problem you have now could just be because they have grown so well and are producing more waste as larger fish. Since goldfish are considered one of the more dirty or high waste producing fish they can as they get larger create some problems. I don't think you are keeping your tank too clean since it can be hard to keep goldfish tanks clean enough when they become large. You do have good filtration. I wasn't really for sure if you did have an undergravel filter. The only problem with them is that they do have a tendency to trap fish waste and decaying food under the plate that is placed under the gravel. That can cause water to become cloudy and sometimes even causing it to become toxic to fish.
Your cloudy water could be caused from several things. It is always hard to pinpoint exactly what is causing it but maybe you can decide if any of these things might be causing your problem. First and usually this is what causes most, is too many nutrients  in the water. Either by more fish waste or too much fish food from overfeeding. Another cause is from medications that destroy beneficial bacteria and and a tank   starts a mini cycle all over again. You could be having this problem since you are having to use ich medication. Also, I noticed that you were having to use Nitra-zorb to help with nitrates. If your nitrates are too high then you probably need to do more frequent water changes to control it. I have only two fancy goldfish in a 29 gallon. I have to do two water changes a week and remove around 1/3 of the water each time. They seem to do better with more clean water. If you do decide to do more frequent water changes start out with small water changes and then gradually increase over a few days. Reason--if it has been a few weeks since a water change has been done, the pH drops, then when you do a large water change pH increases and causes the fish alot of stress and can make them sick. Just be sure to really keep their water clean since they are larger now. You can control most water problems with frequent water changes.
As for the ick--Are you treating long enough? Sometimes it can be really stubborn. Be sure to siphon gravel well and if you do have an undergravel filter you might want to consider removing it since it just might be hiding ich since part of the ich cycle is when the eggs fall into the gravel. Also, be sure to remove any carbon that you might be using in your filters since it does interfere with medications.The medication you are using really should work.
I am not sure exactly why just one fish is always getting the ich. Usually a disease strikes the most stressed or the weakest fish first. I don't know if that is the case with your fish unless there is some reason he is more stressed than your other fish. It could be that he just got the ich and has never really been able to get healthy again before he gets it again due to it not being completely under control in the tank. It probably just weakened him. You should be able to get it under control. Since he is having the problem with ich is it possible to place him in a different tank and treat him? Then you won't take the chance on destroying your beneficial bacteria in your tank from using ich medication and having to cycle your tank again which will make if hard on your other fish. Ich is supposedly always around but fish don't become sick until conditions are right for the ich to make them sick--such as stress or if any change occurs in water conditions.
Just be sure to really keep the water clean and the gravel. Ich could be living in the gravel and reinfecting your fish. Watch out for any changes in ammonia,nitrites and nitrates. Your beneficial bacteria may be slowly killed by all the ich medication and your tank will have to start over cycling again. If so you could try buying either Cycle or Bio Spira bacteria to help your tank establish more bacteria to handle the fish waste load.
Best of luck with the ich control. You've done a good job so far. Keep the tank gravel and water very clean to help control the ich population and use the medication you have if an outbreak occurs again. It should get under control soon.
Hope this has helped,
Karen