Worm Farm Recommendations

Over my 6 year career as a worm farmer I've used a few different designs of worm farm and have a clear opinion of which one I would recommend to anyone looking into setting up a worm farm. The simple answer is use a bath, I've listed the reasons below. Worm farming, in my experience, is all about surface area and volume. The more surface area you have the more space for the worms to be active. Volume is important because it keeps the temperature stable and keeps a huge populate of microbes, which speeds the process. My biggest worm farm germinates everything (including capsicums) all year round because the decomposition keeps it warm.

1. Can-o-worms (or similar)

The can-o-worms is one design of many that are marketed to households with a small amount of space. The are sold as easy to manage and simple to set up. My experience is that this is not true. I found it difficult to keep the worms out of the bottom tray (where the fluid collects) and found that it couldn't keep up with the waste output from two people, even when I mashed everything with the food processor.
Advantages

• small so not much space needed, good for apartment, townhouse etc
• ready to go, just buy it off the shelf, add some worms and you're away (sort of)
• rodent proof
• collects fluid for use on garden

Disadvantages

• small so intolerant of temperature change and large chunks of food. The worms tend to dig down when too warm so end up in the liquid tray
• difficult to manage because the balance of food going in has to be just right
• expensive, not much change out of $200

2. Wooden Box
I made a wooden box, out of untreated boxing timber. It had two lids and a divider so I could feed in one side and then the other. One lid had a handle on it and the other did not so the lid with the handle indicated which side was being fed. The worms migrated through the divider from the inactive (not being fed) side to the active side over a few weeks. The vermicast could then be harvested.

I put everything into this worm farm including onions, garlic, chillies and bread and have not had any problems (other than a mouse infestation). The large volume allows the worms to avoid the things they don't like until they have broken down through decomposition.
Advantages

• Cheap (~$50 of timber and screws)
• Big and therefore stable environment
• Harvesting is easy(ish), just start feeding on the other side (see below)

Disadvantages

• untreated timber rots away in a few years
• no fluid collection (I just move the bin from time to time)
• not rodent proof
• harvesting is a bit awkward because the vermicast has to be lifted out of the box

3. Bath
A bath is simple, easy and cheap to set up. I have two bath based worm farms. One at work in a full length bath, that processes between 10 and 15 kg a week, and one in a shub (a small, square bath) that processes all our household waste. I don't know how much it processes because I don't weigh into it. The full length bath has processed over 200kg of waste so far and we still haven't had to harvest the vermicast.

The farm at work is up on a frame so that it is easy to work. This one is run by a couple of volunteers and me so it needs to be easy to run. Having the bath at waste height, covered by a piece of roofing iron, makes it very accessible and easy. Because of the volume we don't have to pick bits out of the waste. This worm farm processes large amounts of onion, bread and citrus peelings without any problems. We do use a handful or two a lime a week to keep the acidity under control but otherwise its just a matter of dump the waste and leave the worms to it.

Advantages

• cheap - I paid $5 for one and nothing for the other (both from trademe) The timber frame for the work worm farm did cost the better part of $100 but the farm at home just sits on a few bricks.
• large volume - temperature is stable and harvesting is infrequent
• large surface area - can handle volumes of 10-15kg a week or better. My large farm has only been running for 6 months so the worm population has not reached peak yet.
• easy to manage - just spread the waste on the surface and you're done.
• easy fluid collection - I have a pot scourer stuffed in the drain hole (held in place by a cable tie) and a brew barrel underneath collection the fluid. The stand holds the bath at a 15 degree angle to aid drainage. The tap on the brew barrel makes it very easy to put the fluid into used milk bottles for people to take home.
• rodent proof - especially if its up on stilts

Disadvantages

• quite large - requires too much space to fit in an apartment or townhouse (probably needs more than one family's waste to run properly anyway)
• some setup time if placing on a stand. It took me a Sunday afternoon to collect the timber, build the frame and 'plumb' the brew barrel to the outlet.
• harvesting is a bit awkward because spades are square and baths are not

So, if you have the space and the volume (10kg+) a week then a bath is the best way to go. For a smaller system you could probably use an old kitchen or bathroom sink in the same way as a bath, but bear in mind that the volume is important to keep the temperature stable.

Finally, don't spend a lot of money on your worm farm, the worms won't notice if you only spent a couple of dollars on their house.