Okay, here is hopefully the FINAL set of instructions. I'm sorry that it took an ungodly amount of time to get into my head. Please look over these and tell me changes were necessary.
Tank
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Goals
- Cure your fish of whatever is causing their symptoms of pop-eye, fungus and shredded tail fins.
- Successfully cycle your tank with your mollies, by keeping them alive.
Your situation
Your mollies are becoming sick because of your water conditions. You were skimpy on both testing and PWC's before just a little while ago. This over-exposure to ammonia caused their immune systems to be weakened and susceptible to disease, this is why they are sick.
Not all
may be lost however. Using a fungal treatment and a pop eye medication will cure them, along with frequent PWC's between 25-50%. These changes must not interfere with the medicine's ability to dissolve and enter the fish.
You have also, unknowingly, been cycling your tank by allowing the ammonia to go unchecked and with your inconsistent PWC pattern. This presents an opportunity to both treat your fish, and cycle your tank so they do not become sick again.
Cycling
Cycling is the process by which beneficial, waste biproduct-eating bacteria are built up in your tank. These, along with PWC's, get rid of a substance called nitrates. The pattern goes like this.
Fish/Ammonia-inducing substance releases ammonia.
Ammonia breaks down into nitrites.
Nitrites break down into nitrates.
A cycled tank's bacteria colony eats nitrates, but routine PWC's also filter them out.
This is necessary because ammonia, nitrites and nitrates are all toxic to fish. Nitrates are the least toxic.
Your instructions
These are your instructions, specific to you, to hopefully both treat your fish and cycle your tank.
[*]Acquire a testing kit for nitrites, and pop eye medication.
- You will be performing water changes, with respect to the medication until the fish are cured, based upon your ammonia and nitrite readings. Test your water for both of these once a day, and perform water changes, depending on readings, until both are getting consistent readings of zero. (Kat1103 suggests 25% water changes, around 3 to 4 times a week, with respects to medication.) By then, cycling is finished and the bacteria colony has been established.
[*]If cycling is finished and the fish are alive, life returns to normal, and PWC's become more regular. If fish are lost along the way, proceed with the fishless method. This entails the same thing as fish method, but instead just feeding raw ammonia or ammonia-inducing substances to the bacteria inside the tank.
Wait a period of time before introducing new fish to your tank. This will both give the fish some time, if they are alive, and insure that their sickness is gone. Make sure that if the fish are dead and even if cycling is done, that you feed the bacteria ammonia somehow.