@Cadder @rotters Here is a bit of a mini guide and materials to the self watering tubs I made this year.
Summary: My self watering tubs are made by stacking two cheap Ikea tubs on top of each other. The bottom tub can hold up to 9L of water and has a lid which I have drilled a hole in. The top tub sits on this lid and has a hole in the bottom. I thread a piece of capillary matting from the bottom tub, through the hole in the lid up into the top tub through its hole. The potting mix and plant are then placed in the top tub next to the capillary matting wick.
Step 1: Make a hole in the centre of the lid (I used a flat drill bit to get a nice even 2.5cm hole but you could just cut by hand with a sharp knife)
Step 2: Make a hole in the bottom of the top tub (so it aligns with the hole in the lid)
Step 3: Soak the capillary matting in water so it is saturated
Step 3: Take a strip of capillary matting thread through the hole in the lid and into the top tub (making sure you leave enough to touch the bottom of the bottom tub when the lid is on)
Step 4: Fill the bottom tub with water + soluble fertilizer
Step 5: Place the lid + top tub on top of the bottom tub
Step 6: Hold the capillary matting in the top tub up straight and fill with potting mix
Step 7: Transplant in an adolescent Chilli plant
Step 8: Fill once a month / even less with water + soluble fertiliser such as half strength tomato feed
Materials:
Tubs (£1.50):
https://www.ikea.com/gb/en/p/uppsnofsad-storage-box-with-lid-black-s99393107/
Flat drill bit (£2.29):
https://www.ebay.co.uk/itm/121314592235?hash=item1c3ee9c5eb:g:QK0AAOSwYaFWeU~O
Capillary Matting x 10 strips (5.40):
https://www.ebay.co.uk/itm/194193846050?hash=item2d36daef22:g:I7EAAOSwE7tgXzOz
Pros:
+ Significantly reduced watering effort & ability to go away for a couple of weeks
+ No algae growth (as tubs are black)
+ No over / under watering
+ Cheap
+ Simple uniform look (to me at least!)
+ Have grown some of my biggest plants to date
Cons:
- A bit bulky
- Limited ability to increase water rate / decrease water rate (add top watering to increase & remove top tub to decrease / halt water)
- 10cm x 40cm wick seems to not deliver enough water for adult plants when the weather is very hot
- Dimensions of the tubs mean when plants get big then staking is difficult as the top tub is not that deep (I haven't needed to stake this year)
- Water can get super heated in direct sunlight but I havn't found this to be a big issue (perhaps keep shaded somehow?)
- No indicator to show water level (I have a few ideas on how to solve this but not actually tried any yet...)
Six tubs cost me £4 each but if you made 10 they would be only about £3.50
I think that covers it! I did intend to hook the tub up to a gravity fed trough but didn't feel the need to in the end...