haygar

hi all hope some one might be able to help me i have a four foot bow front tank (300 lt) it has been set up four five week it has a hood with light under it , the light is 2*3ft tube it has three under gravel filters and a 1200l/ah external filter on only have 5 small goldfish and 20 white clouds in it about a week ago it went cloudy , my fish seem ok with that but today noticed my temp is up to 23c from it normal of about 18c must have risen over last couple of weeks summer is not even here yet and my temp is up that high what can i do to keep this down . have heard of ice blocks but is there other ways (chillers?) or such not want to spend a fortune or put ice in every day cheers hope someone can help me haygar 8)