Basically, you should do OK if you follow the instruction in the triops kit.
The bigger the tank you use, the better though, the ones that come with kits are pretty small in my opinion.
But it is important to hatch out in no less than 1 litre of water, as with any more water, the triops wont be able to find the infusoria for them to eat.
De-ionised water (available at tescos at the car section for 51p per liter) is by far the best water for hatching them, but spring water works very well too.
If you use de-ionised water, only use it for hatching them (it doesnt contain enough minerals for triops growth), you can top the water in the tank up withc spring water, or tap water that has been conditioned with a water dechlorinator made for fish tanks (like API's 'Stess Coat').
For feeding, you can just use most fish foods, but they need it powdered when they are very small
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