well,
to begin with you might want to read through some of the old post on the archived "old forums" regarding feeding of painteds. while it is true that over feeding can yeiald a problem, in the long run a diet of repto min and roamaine is going to cause just as many. romaine, regardless of what anyone tells you is not really a highlt nutritious food nor is it a natural aquatic turtle food. If you must use things frm the grocery store, tru collard greens, mustard grreens, turnip greens, radish tops, dandelion greens and peas and grapes and strawberries, blackberries, melon, carrot slivers and figs.
By the way, reptomin is no bargain either. Its smells good so turtles and fish eat it but there are much better pelleted foods available.
Really though, what you need to do is introduc variety into the diet.
A much more natural and controllable diet (in terms of ability to provide a wide spectrum of nutrients) would include earth worms, crickets and superworms, frsh or canned fish, boiled chicken, feeder shrimp, cooked snails or clams, water plants such as duckweed, salvinia and anacharis. You can get most of these things by going to one of three places:
a good pet store that sells reptile supplies
a grocery store
a bait shop.
Reptomin and roamiane in the long run will lead to dietary defieciencies and bored turtles.
I actually feed my painteds twice per day on even days and once per day odd days and provide water plants and aquatic insects in the cage at all times.
But you must feed small amounts if you are going to adopt a feeding schedule like mine. Its okay to feed every other day (its probbaly easier on person, harder on turtle whose natural instinct is to search all day for food) but be sure to add as much variety as possible.
And do look into some of the other turtle pellets and fish pellets.
Some that come to mind include:
Mazuri turtle diet
Zoo Med aquatic turtle food
Hikari cichlid staple and Hikari cichlid gold (yes, for fish)
Hikari sinking carnivore wafers
and the ever popular Nasco turtle brittle (which i have had bad lucjk with but which everyone else seems to think is great)
there are others as well. Its probably better to have several different kinds on hand so if he gets bored with one kind you can switch off ofr aweek and then switch back later.