When we used a portable 5000W gasoline generator a few years ago, we set it on the concrete patio.
We used a heavy duty extension cord and ran it through the dryer vent (disconnected from dryer) and plugged the opening with a towel to prevent air from entering the house.
Then hooked up a 6 outlet multi-strip bar to the female end of the extension cord. We then used 3 heavy duty extension cords to run from the multi-strip bar to each aquarium power strip.
The remaining outlets on the multi-strip bar were used for the chest freezer, floor lamp (for lighting) and the boyfriend was able to rig a temporary heavy duty pigtail cord for the furnace (propane) since there was a junction box in the furnace room where the Romex wiring for the furnace power was located.
Just so you know, our generator needed to be filled with gasoline every 2 hours. You also need to perform regular maintenance on the generator as recommended. When we needed to use it 2 years later, we couldn't get it to start and had to replace the spark plug. It's also important to have fresh gasoline available.
There is no real need to keep it covered though I did shovel snow around and away from the unit when we used it.
It's also important to read the literature and follow the mfg. recommendations for extension cord use. A refrigerator would definitely require a heavy duty extension cord and you will want to keep it as short as possible in relation to the generator location.
You can set the generator on the ground, just be sure it is not near any flammable material such as dry vegetation.
You don't need multiple surge suppressors.
Eheim Pimpette #270
Eheim Pro II 2028; Classics Series -2215, 2217, 2260, 2262; Pro 2229 Wet/Dry