Turtles and Tank (Mineral Point)

African side neck female and I believe the other is yellow belly slider male have lived in same tank for years.
I just got them last year was told they were 4 and 2.
They are in a 75 gallon tank on stand with 3 filters.
2 grass ramps.
I love them but keeping tank clean is taking a toll.
Plus only certain places I can put it in my home.
Asking 150$ for everything