Hi Tidat, welcome to HLF.
Haruans will hang out near surface and they will surface for air every now and then. If you're not familiar with the spot, don't just drop your lure straight away. Choose a time when it's quiet, preferably in the morning, sit down by the canal inconspiciously and quietly and observe for 15 mins. Watch for fish breaking the water surface. Haruans hang near the surface when there's no disturbance, if you see a surface break is that is of moderate size but gentle, it's a good chance it's a haruan. It will usually hang near the surface after or swim back into its hiding location. Take note of the general direction it swam to. You may have to observe it doing this for several times to get a good picture of where it is hiding. From there you can plan on your choice of lures or strategies.
Another way to test for presence of haruans is use of baiting and vibrations. If the canal water isn't flowing very fast. Take some bread and toss near where you think the fish might be or toss it near small fishes that are visible to you. The bread toss alone can sometimes cause the haruans to come out to investigate, and if that's not enough, the sound of the small fishes feeding on the bread will further entice the haruans to come out.
Alternatively, if you have a pole rod tie your frog lure or any type of bait you like and simply drop it along the canal bank. Tap the bait on the surface, if a haruan is there it will usually strike. The difference between this and casting is that it gives the fish more time to hit the lure and the positioning of the drop is a lot more precise. You can use this method to sweep the entire bank if you have the patience.
Many anglers neglect the importance of locating a fish, and cast blindly hoping for a bite. If you're able to locate the fish, half the battle is already won.
recently I have started to target specific fishes and caught a soon hock after a week of luring... But now I wan to get a Haruan. Got a bite using my frog lure but failed to land... 
saw a canal with many baby Haruans but can't find their parents... Any tips on getting Haruans? I'm fine with anything that helps.
