Even though bleach does work i personaly wouldnt use it knowing that any amount is toxic to plants,no matter how small the amount,peroxide is alot more money but is much safer.
The best thing you could do is to get the rez temp down alot more than 70 degrees,if your chiller cant get temps down to 60 or lower than you need a bigger model.
I keep my 55 gallon rez's between 58 & 60 degrees at all times & dont ever fight slime anymore,get your rez as cold as you can,if you cant afford a bigger chiller than ice works but ya gotta get temps way lower than 74 degrees.