When it did get really hot here in the summer, I would just leave the tops on the aquarium open. This would drop the temp down under 80F as my room has an overhead fan. The most important thing to remember about those warm times is good aeration. I have a bubbler in the tank that runs in the summer. Because it's rather noisy I usually turn it off in the winter.
Ooh really? Have you got a recipe?
I most certainly do have recipes! I like the babyfood ones because all the food is pre-blended (blenders scare me). With those it's just dump, mix, and set! This particular one is what I use. I pulled it from the goldfish forum I like.
3 jars baby food, green veggies (only 1 sugary**)
1/2 cup boiled hot water
2 envelopes of gelatin
1/2 adult multivitamin (no iron)
1 1/2 oz salmon (drained if from can) (half a can) <-- I find it helps to chop this up a bit
1/2 teaspoon pure garlic powder *
Dissolve 2 envelopes of gelatin in 1/2 cup hot, boiled water. Mix veggies, salmon and crushed pill stuff in a small bowl. Pour gelatin/water mix into the bowl. Stir well (it helps to have one person stir while another pours). Pour into a flat container so it's about 1/4" thick. Put in fridge to gel. Once gelled, cut into pieces about 1/4"X1/4". I then put 14 pieces (1 week's supply) into small snack size baggies and lay them flat to freeze in the freezer. When they're all frozen, I place them all in a large size baggie (which keeps them all together) in the freezer.
*optional as it does make the food smell like garlic
**sugary veggies include peas, pumpkin, carrots, ect
That is for adult (over 3 years) goldfish. For younger ones, do one part protein (fish) to 3 parts veggies.