You have to treat the gerbils, the cages & the room.
You have to temporarily remove the gerbils from the house before you de-mite the house. Pets & people should not remain in the place during fogging.
You will also have to find another place for your fish to live for the fogging day.
The link below from the American Gerbil Society has information on dealing with a mite problem.
This website tells you how to do a de-miting without professional help. However, since you have a sever infestation, even on a fish tank & a piece of furniture, you may need to employ some professional help – specifically, a local veterinarian for "Small Animals". Call around, ask if any local practices have a S
In addition to their advice, I’d add:
You have to treat the gerbils, the cages & the room.
You have to temporarily remove the gerbils from the house before you de-mite the house. Pets & people should not remain in the place during fogging.
You will also have to find another place for your fish to live for the fogging day.
The link below from the American Gerbil Society has information on dealing with a mite problem.
This website tells you how to do a de-miting without professional help. However, since you have a sever infestation, even on a fish tank & a piece of furniture, you may need to employ some professional help – specifically, a local veterinarian for "Small Animals". Call around, ask if any local practices have a Small Animal specialist, & go there.
In addition to the AGS advice, I’d add:
1) I suggest you take your gerbils to the vet – in plain plastic transport cages (buy a couple in the pet store, the ones with a handle) – & check them in for de-miting & a short boarding stay while you clean the room. The whole process should take a few days.
2) At home: discard all gerbil bedding, including open bags (see the website). Put all furniture & toys from the cage in a covered Rubbermaid storage box. Put it on your porch in the cold. We’ll get back to that later.
3) Follow the directions on the website for cleaning the cages.
4) Go to the hardware store, or Lowes or Home Depot: Find an insect fogger bomb for use in the house. You want one that kills mites & spiders, as both are in the decapod family, & the same stuff kills them both.
You can check with the vet for a suggested brand.
NOTE: Also ask the vet if a piece of a commercial cat flea collar attached to the upper corner of the gerbil tank will a) prevent any new infestations; and b) be safe for the gerbils.
IMPORTANT: Are you renting a room in a larger house? Is it your parents’ house? It is a dormitory? If it?s a single-family house, you will likely have to insect-bomb the entire house you live in, so find out what the approximate square footage of each floor is. Insect fogger bombs are made in different sizes for various square footages.
5) After you bomb the room or house, wash anything that has dead mite bodies on it (sheets, blankets). Vacuum all other surfaces, both hard surfaces & upholstered furniture – take the couch apart (if you have one) to get the corners.
6) Hose off all the furniture & toys before you bring them into the house again. If you don’t have a hose, dump water on them by the bucket. Rinse out the Rubbermaid box.
Bring the Rubbermaid in & boil the furniture & toys for 5 minutes. Spray them with the stuff the website suggests.
Anything with cloth parts should be washed in hot water or discarded.
Then you can reassemble the room.
Between the website, the vet & general advice, you should be able to fix this.