Citrus and onions in wormeries
Periodically the question of adding onion and citrus to wormeries is raised by people new to worm keeping. There is a lot of information on the web and I have been prompted to list some of the sources that may be of interest. This is contained with more genral infomation at http://www.carryoncomposting.com/142941459 or by following this inernal link if already on carryoncomposting.com Wormeries
The general advice to the public seems to be that the onion family and citrus fruits should not be added to the wormery as they increase acidity and that as high acidity levels will kill the worms it is better not to add these materials. However, many sources report that feeding acidic materials in moderation may not cause problems but it would be advisable to measure the pH regularly and add lime as necessary to keep the material at or near pH7.
It may take longer for the worms to eat the dry outer layer of onions. https://www.epa.gov/recycle/how-create-and-maintain-indoor-worm-composting-bin#feed
If added to the wormery in large quantities onions said to burn the skin of the worms. https://www.wormcompostinghq.com/feeding-your-worms/
Onion skins and scraps can also be added with caution to a conventional compost bin traditional compost bin they do not negatively affect the composting microbes present in the bin but their smell may attract pests and unwelcome wildlife. In both compost bin and wormery they are best cut into small pieces before being added so that they breakdown more quickly. Worms do not like the smell of the onion family so, when given a choice, they may be left uneaten until they begin to rot.
Adding shredded paper, newspaper and cardboard may help control the onion smell and reduce the risk of attracting pests. https://homeguides.sfgate.com/can-compost-onions-72087.html
The situation is similar with citrus peel the advice is do not add it to the wormery but if it is added the worms will leave it until the peel to starts to decompose and then eat them.