I am sure that you have come to realise that every second post has the word "Ethical" in it. Then again, there shall be words like don't support Petshops, BYB (Back Yard Breeders), Feeder Breeders etc, etc, etc.

This is a never ending story within the community and to be honest, it can be exhausting when clarity is never fully given or rather one sided points are provided for what is ethical and what is not. 

Ethical is providing Food, Water, Clean Bedding, Space, Enrichment to the rats in your care. 

A rat appropriate diet - this may be majority Dry Mix and occasional Wet Meals or majority Wet Meals and occasional Dry Mix - the condition of a breeders animals should always be something to consider.

Water - Clean water to be available at all times, if using water bottles, they should be free of algae growth etc. If using water dishes they should be in a position in the cage whereby they shall not be soiled by faeces and urine, once again should be free of any algae growth.

Bedding - This is a personal choice for each individual and as long as the bedding is not causing any irritation to the rats and is perfectly safe for rodents then no more needs to be said.

Space - Cages or Tubs can be used, as long as there is no overcrowding and sufficient space for the colony to be on the floor space at the same time and move freely, then judgements should not be passed. Ventilation should be adequate as well, to ensure that air is able to circulate.

Enrichment - This is where some breeders will try and outshine a fellow breeder, by trying to provide the best of the best. Basically anything that adds stimulation to the rats daily lives is sufficient, an empty box, brown paper bag filled with newspaper, a branch or rope to climb on. Perhaps scattering their food in different places within the cage etc.

The following is linked to each other: Conformation and Health - all breeders shall constantly list Health as a priority, but the truth of the matter is, conformation and health go hand in hand. If a breeder is constantly producing pinched faced rats, litter after litter, then they are not breeding to improve the line or better the health, but merely breeding to produce more rats. 

Medication / Euthanasia - these work hand in hand to an extent. Some breeders shall choose to medicate rat/s in their colony, whilst others will choose to humanely euthanize any ill rat/s within the colony. This is a personal and individual choice made by each breeder as to what is suitable for them and what they are comfortable with. The IMPORTANT thing to note is that no rat/s should suffer for any length of time. If you can't Medicate then Euthanize - If you can't Euthanize then Medicate!

An Ethical breeder should never use a sickly rat for breeding purposes and more importantly not use a known sickly rat and still do a pairing. This is something that many will overlook, but the only time that an ill or previously medicated rat should be considered for use in breeding, is if it is the last of its kind and the  variety needs to be secured by this single rat.