How to stop a cat from eating dog food?

I put this question on here earlier and I got a lot more lecturing than actual answers, so I'm doing this to try again, with more details.My cat, a male domestic longhair, has taken a sudden interest in my dogs food. My dog (a male beagle) is really picky when it comes to food and only eats a little bit at random times. Because of this, we have to free feed him. We've tried feeding him at certain times, and he hardly ate anything and lost a lot of weight (he was thin to begin with). So then we tried to put the bowl up on a raised platform, but he's too little to reach.I know that dog food is very unhealthy for cats, seeing how cats require more protein, vitamin A, and need amino acids for eye health and fur growth, so filling up on my dogs food is bad. They're both fed blue Buffalo (obviously dog food for the.dog and cat food for the cat) because its the only one I could find with real ingredients and not corn byproduct. (Plus my vet approves).So without the lectures that I must be feeding them bad food, or have a badly trained dog, can anyone help me?Thanks in advance, and I apologize for any spelling or grammar mistakes. I'm writing this on my phone.

I have a terrible time keeping my youngest cat out of my dogs food bowls. My dogs are fed on a schedule except my smallest dog but my cat is so big that my smallest dog is literally pushed out of the way by the cat. I got permission from my landlord and installed a magnet controlled dog door in my laundry room door. He wears his collar with a little magnet fob attached and can go in and out of the door but the cat cannot. I believe this is the one I boughthttp://www.petguys.com/-035368002590.html?productid=-035368002590&channelid=FROOG&utm_source=CSEs&utm_medium=GoogleShopping&utm_campaign=PetGuys

Reported for spamming with the same question. You got a LOT of good answers and advice the first time you asked this.Just because the dog eats Blue Buffalo still doesn't mean it's food the cat is OK to be eating. Dog food lacks Taurine and without it your cat will go BLIND. It also has too much fat and way too little protein. AGAIN - stop letting your dog run the show. Feed it twice a day and remove the cat from the room. How freaking hard is that? Do you think your dog is going to "starve to death" and refuse to eat when you make him wait to be fed? If so LOL!!!!!!!!!!!!!!!!!!!!!!!!