Shaz, The OCLT is an overnight chlorine loss test. It is done at the end of every SLAM to conclude that all algae is killed.
Your water can be clear but still have organics consuming chlorine.
You need an FAS DPD test which you can add to your kit from TFtestkits.net. The kit you have now can not perform the OCLT.
As far as algaecide goes, you don't need it. Like pwstrk stated, as long as you keep the FC up and in relation to CYA, it is not needed.
Have you read Pool School?