When I used substrate for the rabbits I found aubiose to be an excellent product both in terms of absorbency and price.
I didn't get on with fitch at all. The bale I got definitely couldn't be described as soft and fluffy.
For the mice I either use bunny bed o'linum or hugro hemp bedding both from zooplus. Both more expensive than aubiose but lovely and soft and dust free (although I found aubiose fine for the rabbits).
I don't know where you read that citronella is safe but the oil is generally regarded as something rabbits shouldn't come in to direct contact with. I'd actually avoid anything scented, personally.
An extreme example, but one study found A dose of 1 to 4 mL/kg given by stomach tube in rabbits caused paralysis, coma, and death.. If as little as 2ml for a small rabbit can cause death, I do wonder what harm ingesting and inhaling small quantities could do to the kidneys over time.
Confusing then, as citronella is from the lemon grass plant and lemon grass supposedly safe for rabbits:
http://www.gardenmyths.com/citronella-plant-keeps-mosquitoes-away/
BTW, I wasn't advocating letting rabbits come in direct contact with any oil. With all essential oils, contact with undiluted oil is not recommended for animals, humans or furniture! A lot does come down to the concentration and amount of exposure to the oil. Those Glade air diffusers are horrendously toxic as well. There's a ton of information about the dangers of air fresheners...
I had a little dig around the Net this morning and located the article you referred to:
http://www.drugs.com/npp/citronella-oil.html. The following is from there:
<Adverse Reactions
Citronella oil has been reported to cause contact dermatitis in humans. 3
Toxicology
Animal toxicity studies have shown that citronella oil has an LD 50 in mice of 4600 mg/kg and in rats of 7200 mg/kg. A dose of 1 to 4 mL/kg given by stomach tube in rabbits caused paralysis, coma, and death. At least 1 case of death has been reported in a child who ingested an unknown quantity of citronella oil. A review of 5 cases of childhood citronella oil poisoning suggests that dilution of the oil following ingestion may be sufficient to treat most cases of ingestion and that emesis may be induced with a relatively low risk of major pulmonary complications. If spontaneous vomiting has occurred, observation for respiratory symptoms is required. 10>
Another interesting article mentions the toxicology of geraniol as well as citronella and both as being irritants:
http://www.pesticide.org/Alternativ...est-solutions/plant-based-mosquito-repellents
<Geraniol
Geraniol is an alcohol found in many plant oils, including citronella, lemongrass, and oil of rose.8 It is used as a fragrance in personal care products and detergents and also to flavor drinks, ice cream, and candies.9>
There were some other interesting articles I came across concerning essential oils and animals, and it would be very interesting to see what complementary practioners who treat animals have to say about the subject.
http://www.optimumchoices.com/animals_essential_oils.htm,
http://www.peta.org/living/companion-animals/abcs-cruelty-free-flea-control/