Urgent Care :: Turtle's Skin Turned White

[RESinSpain]

Hello, turtle people!
I came to Spain about a month ago for a job. I am staying with a family who has a turtle, and I think it is a RES.
When I finally came across the turtle about a week and a half ago (I had been looking for him since I knew they had a turtle), he was outside in an aquarium with just a few centimetres of water in it and the water was BEYOND disgusting.
It was completely opaque with green-brown sludge and smelled absolutely awful. It was literally just the turtle in an aquarium with a bit of very dirty water - no heat or light source, no filter, no basking platform, nothing!
I felt so bad for the poor little thing, so I decided to clean the tank myself this past Wednesday. I didn't use any cleaning agents because I didn't want to use something toxic by accident, so I just emptied the aquarium, scrubbed it and rinsed it with clean water, and put in new water aiming for room temperature.
Yesterday, I noticed the turtle's skin looked a little pale and he was closing his eyes a lot.
Today, his skin on his face and forelegs is very white and there are chunks of white stuff coming off, he is keeping his eyes closed most of the time, and he has fits every now and then where he appears to be coughing and he thrashes about like crazy.

Turtle's white face

Chunks of white stuff hanging off

He is not my turtle and I make a very small salary so I can't take him to the vet, but I went to a pet store today and got a UVB lamp, a submersible water heater, and a basking platform (€80 - ouch!). When I came home, I changed his water again and installed all the things I bought. I think the platform is too small and I didn't get a heating lamp so I will have to make another trip and spend even more money.
I am still very worried about the turtle and down't know what's wrong with him. I will attach pictures and any help would be greatly appreciated!
I don't know if this makes any difference but he (they say it's a male but I don't know) is an adult turtle and is reasonably large, about

[RESinSpain]

I meant to add, his shell is about 6"-7" long.

[steve]

I'm not sure what's happened... but you have a big job ahead of you. First, take the turtle out and let the turtle dry off. Clean the tank. Replace all the water. Soak the turtle in warm water and gently scrub the shell, and wipe the skin and shell. Give him a good inspection. It's possible the white stuff is fungus or an infection from neglect but this could also be some abuse. Is it paint? Chemicals?

Alternatively... take this turtle to a rescue or leave him at the vet. It's something to consider. I hope you can figure something out!

[RESinSpain]

Thank you! I will follow those steps.
He looks a bit better today. There are no white chunks hanging off his skin, he is slightly less white, and he hasn't had any more fits.
However, he is now constantly rubbing his face and biting at his forelegs.
I don't think it's paint or chemicals. I really don't know what it is. The white stuff is like a thick, greasy paste and doesn't wash off easily.
The family is saying that it's my fault because I changed his water and they have had him for 13 years and never change his water except in the summer. Is it possible that this is my fault? Even though I didn't use any chemicals or cleaning agents when I cleaned the aquarium?

[steve]

From what you've described, its not your fault. If that white material is normal for them, then they were not caring for it properly. If could be grease or fat, perhaps they dumped something into the tank. How are they feeding it? What's the tank like?

The turtle also looks to be female. If you're only there temporarily, then you should consider surrendering her to someone or a facility that can care for her.

[RESinSpain]

It's not that the white stuff is normal. They said that's never happened before, but they said that since she turned white after I cleaned her aquarium, it must have been something I did. They say they only clean the tank in the summer (and then leave it dirty during fall, winter, and spring because they say the turtle's hibernating and they don't feel like cleaning the aquarium since it's too cold), and they said that since I cleaned it in the fall, I must have messed with what the turtle is used to and caused the white stuff.
On a good note, the turtle is just about back to normal now. I have no idea what happened!
I don't know what they feed her, or if they feed her at all. Can you recommend a type of turtle food that I could buy for her?
As for your questions about what the tank is like, this is how it looked a couple of days after I cleaned it the first time:

Since then, I have cleaned it again and added more water, a basking platform, and all the other things I bought. I am also keeping her in my room now.

[steve]

I'd do frequent cleanings to make sue you get as much of the stuff out as possible. As for food, I'm not sure what's available there. Mazuri, Reptomin and Omega One are what we suggest. Hikari might be found internationally. Veggies are also good: redearslider.com/plants.html