After the case, David Sharod, 37, criticised the RSPCA for bringing the case, saying: 'It's been a total waste of time and money. We all put money in their pot but then they have to go and do this.'
Legal experts put the cost of bringing the case at more than pounds 8,000.
He was acquitted by Maidenhead magistrates after producing a book written by an RSPCA expert that said it was safe to leave fish unattended for up to two weeks.
Mr Sharod, an electrician, said: 'I am totally sick for myself and my family. The case has caused us a lot of grief.
'If it had gone the other way, it would have meant people keeping fish couldn't go away. They wouldn't even be able to go to work.'
The RSPCA decided he had abandoned the South American sucking loach and sucking plec when he left his home in Maidenhead, Berkshire to run a pub for a friend.
He denied two charges of abandoning the pets in circumstances likely to cause them unnecessary suffering on 23 October last year. He said the fish ate algae in the tank and did not need feeding every day.
The court heard that police put tape seals on Mr Sharod's front door to see if he returned.
Lisa Chapman, 23, an unemployed waitress, of Herne Hill, south London, was fined pounds 80 and ordered to pay pounds 50 costs by magistrates for leaving her pet rat Ziggy for six days without water and only a tiny piece of cheese to eat.