I have 3 tank raised Kamohara blennies. They were in a 2o gal qt with a glass canopy. They are skittish and jumpy fish. I received my custom all in one tank and I needed to set it up where the 20 gallon quarantine tank was. I’ve moved the Blennies into a 10 gallon cube. I put some egg crate light diffuser on top of the tank to keep them from jumping out. I did not think the Blennies could fit through the holes. The first night when the lights came on I heard a slight rustling sound from the plastic egg crate and then a splat. One of the blennies jumped through the egg crate and was on the floor. I rescued him/her and put them back in the tank. The next morning the exact same thing happened. I got some clear quarter inch mesh and put that over the egg crate. That kept them from jumping out of the quarantine tank. It also gave me an idea regarding how I can make a cheap easy top for my new tank. All you need is a 2x4 foot light diffuser panel,cutting pliers and 4 inch white or clear cable ties. BRS sells clear mash screen in quarter inch and 1/8 inch hole size. Home Depot sells the rest. Total cost is about $20. The first thing I did was to cut some clear acrylic strips and glue them around the perimeter of the opening of my tank. I didn’t want this to be permanent in case I didn’t like it so I just used silicone. If you have a rimless tank you can buy clips from Amazon that fit on the rim and do the same thing. The next thing I did was to cut a piece of light diffuser was a little larger than the opening of my tank. Then I cut it to fit just inside the opening. The next step is to cut out the middle of the diffuser to make a frame. I leave it a little wider in the back to allow for cutouts for equipment. The next step is to take some of the mesh in cut it to the right size and then secure it with the cable ties around the periphery. It works best to do one side and secure it then put some tension on it while you secure the other side so it gets rid of some of the wrinkles. Use a cable tie approximately every inch or two. I ended up with about double what you see in the above picture. After you have it secured you can cut the cable ties short. I cut them flush. That’s it – now you have a top that will keep the fish from jumping out and still let your light in! One last thing -I ended up putting another small piece of acrylic at each corner for additional support. (Not shown in the last pic.