If you're applying for a Fiancée visa he needs to be in profit for around £2000 to be on the safe side, with no negative on the supplied statements. If a Spouse visa, you can go as you are with the bank, but still it's best to be in profit.
If he explains the situation to the bank manager, he could give him a 6 month loan to tide him over, you'd the have to wait for the debt to vanish off the statements.
Don't give them any reasons on the application to deny you.
