Backyard Aquaponics
A place to discuss aquaponics

This is my second system and I want to make it for as little as possible outlay..

It will consist of 5 blue barrels (50L each I think, sourced from work @ $2.50 each) one as a tank and the other 4 as GB's
I will use rocks from the beach as media, including porous light stones (they look like bacteria would have lots of places to live)

I want to record all costs associated with this new system I am building to help others who want to build a low budget system

I still require 19mm joiner barbs and 19mm top hat grommets, I will update my table as I progress

I know you're a bit latitudinally challenged down there in Tassie, so there's probably less chance of it being so, but are you certain these Porous rocks aren't broken up coral skeletons?

...and the 22mm spade bit, that's not for the top hat grommets is it?

I think they are Pumice stones



NO, I believe the top hat grommets already have holes in them, I will use the spade bit on the drums, as these don't have holes in them..

Fittings for my pump

I had a good laugh at your humour concerning the grommets, jwhittak98, but then I realised that maybe you weren't joking.
Mr Damage may have been concerned that you were planning to use a spade bit rather than a hole saw to make your holes for the top hat grommets: I certainly am!
If you want a leak free takeoff then I strongly recommend that you borrow (to keep costs down) a hole saw and arbor and save your spade bit for less precise timber applications.

so a spade bit is not good for this application?
a hole saw is expensive, at least for one that will do a better job than the spade bit.

I wouldn't risk using a spade bit on the drum because they have a tendency to cut a fairly rough hole that can be difficult for a simple top hat grommet to seal. You might be lucky, or you may have better quality spade bits than I have, but if it was my drum that I was putting a hole in then I would use an el cheapo hole saw before I would consider using even an expensive spade bit for this task.
You can generally buy inexpensive hole saw sets at large hardware stores or online.

hmm something to think about

Yep... On thick plastic you might be able to get away with using a good quality spade bit if you have a steady hand, but you may need a small 1/2 round file to finish the back end of the hole off neatly.

I know a 22mm hole is recommended for the top hat grommets, but it tends to provide a not-so-snug fit that can leak... trust me, I drill out dozens of pots etc every week for top hat grommets. I tried finding a 21mm holesaw, but it's not a common size, so they're hard to find and usually expensive when you do, last time I found a tool shop that stocked them, they were twice the price of a 22mm. So I bought a 20mm and I finish the hole of with a small 1/2 round file to about 21mm, it doesn't take much. Work your way around the hole in smooth arcing motions so you don't end up with an egg shaped hole.

Have you tried imperial??
13/16 would be close to 21mm if you could get it

If you don't won't to buy the hole saw you could clamp two pieces of scrap timber either side of your FT wall and use the spade bit then. Obviously you need clamps and the required hole would need to be in an area where you could use the clamps. The timber just acts as a guide while drilling.

I gave the spade bit a go to see the results It made a mess

Oh, that is an easy fix, it is called a new barrel.

that was a practice hole in a spare lid no need for a new barrel...

I learnt that you can use a spade bit just go slow


I pulsed the drill and not to fast, top hats sealed very well

I assembled my system today. need to add media and do some fine tuning.. will post pictures soon