MY Friends tank is trying to overflow!! Help11

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The tank has been running for 10 years. This is the first time he has had troubles. The tank was running fine. He did a water change a few hrs ago and now its trying to over flow by sucking the sump dry. I had him ck to make sure the teeth weren't clogged. I had him try a new pump to make sure the old one wasn't going nuts on him.TY for your help
 
He found it. It was the tiny hole on top of his stand pipe. It was stoped up with salt creep i think he said 
 
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