How do you clean a tank that hasn't been cleaned in a while?

[VioletThePurple]

I've decided that I wanted to help out with my parent's turtle tank. However, I'm afraid that with me doing newly frequent water changes it could harm them. For context, the tank has turtles and goldfish. Which will go into a pond eventually, but it's a big project. I don't want to harm them by replacing clean water that they're not used to. I don't know a safe method to do this.

 

[mbsqw1d]

I've decided that I wanted to help out with my parent's turtle tank. However, I'm afraid that with me doing newly frequent water changes it could harm them. For context, the tank has turtles and goldfish. Which will go into a pond eventually, but it's a big project. I don't want to harm them by replacing clean water that they're not used to. I don't know a safe method to do this.

Hi do you have any water test kits? You want to be checking what the parameters are in the tank and also of your tap water. Parameters such as PH, nitrate, nitrite and ammonia. Once you know these you'll be able to have a clearer understanding of how to go about replacing their water

 

[Colin_T]

If the tank hasn't had a water change for several months, do the following.
10% water change and gravel clean the substrate every day for a week.

Then do a 20% water change and gravel clean the substrate every day for a week.

Then do a 30% water change and gravel clean the substrate every day for a week.

Then do a 50% water change and gravel clean the substrate every day for a week.

After that just do a big water change and gravel clean once a week.

Make sure any new water is free of chlorine/ chloramine before it's added to the tank.