OK looking into it, copper does not kill them. Anyone know how to get the water temp up very high?
You could try google-ing Electric Charcoal Starter
Just be careful, those things were designed to ignite charcoal. You may blow past 70 C, melt the silicon in your tank and watch as all four walls comically fall at the same time and dump scalding hot water everywhere. (Protip: Do this outside.
And regarding bleach, I'm not an expert and I'm too lazy at this point to look it up but, while the bleach will most likely kill the live ostracods it may not kill the eggs. And it just takes a few missed eggs to get the whole ball rolling again.
Personally, I'm in agreement with everyone else. Those ostracods are a sign of a good ecosystem. If there's an overabundance of ostracods it means there's an overabundance of food for them. Correct the food problem and the population will go down.