Security Deposit - Apartment is covered in grease!!!!

[Bob Mazza]

Looking to help from the BP community in figuring out how much of a security deposit I should hold back. I had tenants move out of a small studio apartment I have about 3 weeks ago. When I went to get the keys the apartment was left in terrible condition and I advised the tenants that they need to clean if they want their deposit. They did but not to my standards.

Here is how things looked...

• The shower may not have been cleaned for the year and a half they lived there. They tried to clean after I asked them but the new glass shower doors were covered in soap scum and crud between the doors. I ended up cleaning that. 
• I found a leak in the ceiling that appears to have been there for a while but never reported. Opened the ceiling fixed the leak and had to repair the ceiling - under the ceiling where the water collected the floor finish is clearly gone and I believe it is from the leak
• The apartment was generally dirty everywhere requiring a vacuum and mopping, I ended up painting the place.
• THE WORST PART WAS THE GREASE!! Not only was the oven covered in a thick layer of grease, the countertops were THICK with it, the window in the kitchen was covered, the microwave, refrigerator, sink, cabinets, floor, EVERYTHING!!
• Cleaning grease is a lot harder than I thought, special chemicals still require multiple cleanings...Moving the fridge was an eye opener as the floor was filthy with food grease and mouse droppings they chose not to clean. Under the sink was disgusting as well but not a grease problem.
• Furthermore, this is a tenant who complained about mice. When I saw that literally everything was covered in cooking grease I now believe the problem was caused by them. I paid an exterminator 500 bucks to come out and really I believe their lack of cleanliness caused this.

I had the apartment repainted, cleaned everything replaced a microwave and it took longer than any apartment I have ever had to turnover. Their security deposit was $950 bucks - they really did not take care of the apartment but lived there for just under a year and a half.

I have never held back anyones security deposit but do not feel I can give theirs back, they really did not take care of the place - Can you all help me figure this situation out. I want to give these folks an answer and would love to hear your thoughts.