I made this Homemade Koi Shaped Cake for my oldest daughter's 24th birthday. I found ideas on this website. I made the homemade fondant (first time ever working with fondant) that I found on this website along with looking at You Tube videos on how to make fondant. The recipe I used was 1 bag of miniature marshmallows, 1 bag of powdered sugar and a tablespoon of water. Experimented with rolling it out and found that you need to slightly chill the fondant before using or it gets to soft and tears easily. You should also use Crisco on your counter/surface to keep fondant from sticking as you roll it out.
The bottom cake was dark chocolate cake with a layer of blueberry preserves in the middle and then I used paste food coloring to tint the fondant blue. Left over scraps were then tinted a darker shade of blue to use as bubbles. Fish part of cake was a strawberry flavored cake. I made a 12 inch cake with one box of cake mix. I drew the shape of the fish on a piece a paper and then used it as a template. I cut out 2 fish from the 12 inch cake and place one on top of the other with frosting as glue in between and then proceeded to carve the shape of the fish from there.
I then put a thin layer of frosting over the top of the fish. I colored the fondant on this one cream. I used the end of a vegetable peeler to make the fish scales (it had a curved u shape at the end, but any semi circle could work). I then made the fins from the left over cream colored fondant. I chilled the fins before adding them to the cake. I used a small amount of vodka (it did not change the taste of the fondant as it evaporates) and the food coloring paste to create the paint for the fish.
The eyes were made from fondant as well. I also had a edible sugar shimmer powder which I brushed over the paint once it was dry. It was a lot of fun to make!