Do you have a 30+ gallon laundry bin? When I had to do similar things, I just fill the bin with tank water, hang on their filter[at least one of them] and then the heater.
You can empty all the water until you reach the substrate. Leave the sand/gravel in. If you have live plants, put them in the bin with the fish. Make sure you seal the tank, filters and bin where the fish are in so NO paint goes into them. When you move the fish back, make sure the temp is the same or float the fish. The new water should be as close to the temp those fish require.
You can empty all the water until you reach the substrate. Leave the sand/gravel in. If you have live plants, put them in the bin with the fish. Make sure you seal the tank, filters and bin where the fish are in so NO paint goes into them. When you move the fish back, make sure the temp is the same or float the fish. The new water should be as close to the temp those fish require.
