BTW these are the cat's meow when it comes to drains for small fish. The slots are between 1/16th and 1/8th inch. Slots are more resistant to clogging than holes and you need that with the frequent feeding of fish fry and fingerlings that produce a lot of waste. I use shower drains for larger fish.
They're PVC ventguards that I got from Menards. As you can see they come in different sizes. I think there is also a 4 inch. I use 3 inch PVC for all my tank drains so I use the 3 inch size.
