I tried the same heater and could not get good temp from it. I was thinking what could make instant hot water. Coffee maker, looked on e-bay found this.
Water Heater, 120 VAC, Inline, 1/4 I/O, 186 F Max, Bunn.
This item is made of all stainless steel. It is approx 12 inches long and 2 inches wide. It has 120 VAC spade electrical connections on one end and a remote bulb thermostat on the other. There is a Temperature overload on the top. Water inlet and outlet are welded 1/4 tube fittings for clamp. This unit came from Bunn Coffee water heating units.
It was $19.00. on e-bay. Had to replace the thermostat, the one that came with it would only go down to 145 deg. to hot. Used a thermostat for a hot water heater. I set it at 110 and I am getting 85 deg. at the nozzles. You can get allot hotter if you want 110 works good for me. I have it coming on the same time as the pump, getting 85 deg. in about 20 sec. at the nozzles. I run it for 5 min. two times a day on two cages. After 20 sec. the temp stays the same at the nozzle heads. I don't think you would have problem with 5 cages. After you get it set up the only thing you have to do is add water to the 5 gallon bucket.
Hope this helps.