The work has started in earnest. First the cleaning. Someone suggested I use CLR, but after taking a good look at the material data safety sheet, I decided I didn't want to take the risk. My first try was with good old vinegar. I sprayed some on one evening and left it overnight. Then, using very fine steel wool (no soap) and more vinegar, I scrubbed the inside and outside.
It still wasn't perfect, so I moved on to my next option - isopropyl alchohol. It does the same job as metho, except that it has no additives and thus evaporates completely, leaving no residue. Nonetheless, I hosed it out a couple of times and left it in the sun to dry. If the vinegar and alcohol didn't kill any nasty microbes, the sun would definitely finish them off!
With the tank as clean as it was going to get, I began to cut some wood for the lid. As I did, I mused on ventilation. I didn't like that the only air would come from the top. I discovered, with the correct instructions, a diamond-coated hole saw and some bravery, that it's possible to drill holes in glass. I bought a 25 mm diamond-coated hole saw from Bunnings, took a deep breath and started drilling. The operation was successful - unless the glass shatters two weeks down the track.
I won't go into precise instructions here. There's some good info on the net. I used
Drilling holes in aquariums (PDF) as my main guide, as well as
Drilling methods and some advice for diamond drills and
How to use diamond core drill bits. Never use this method to put holes in tempered glass - it will shatter - and don't drill holes too close together or near edges. I've posted some pictures of the process below.
Drill with the diamond-coated hole saw:
All set up and ready to go:
When you use a diamond-coated hole saw on glass, you need coolant or you run the risk that the glass will get too hot and break. I opted to use a trickle of water from a garden hose. Please note that the trickle depicted is too light - you need a slightly faster flow than this:
I cut a
very rough drilling template to stop the drill from slipping before the hole was deep enough to give it a good footing. I used a bit of Blu-tack on the back to help stop the template from slipping, although I did still need to hold it down:
By the way, the masking tape on the other side of the glass is to stop the glass circle from dropping to the other end of the aquarium when it breaks off. It also minimises the chance of chipping and catches any glass shards. Beware the glass shards - they're sharp!
I drilled four holes in each side at the bottom. I didn't put them all in a row because I was concerned about weakening the glass along a straight line:
After that, I hosed out the aquarium, scrubbed away any remaining adhesive and left the tank outside to dry. Now that I've successfully done the drilling, I'll go get the vents I've picked out, as well as some other materials.