Well, out of funds is clear enough for a message I think.
The bigger question is, why is that error message captcha protected?
If it cannot pay, putting a captcha in front of the error message only maximizes frustration for the users.

As a suggestion (and as seen on other sites) I'd say, either make sure it NEVER runs out of funds, or put the information of how many funds a faucet has in stock on the main page of the faucet, so users will even before making claims already see they will not get paid (at least not at this time).