Last time i fished in Pandan canal was around July 2004, at that time it was swarming with jaguar guapote (Parachromis managuensis).
Other species caught include tilapia (Oreochromis sp.), common carp (now rare), luohan, baung catfish (Mystus gulio complex), and African sharptooth catfish (Clarias gariepinus), there is also the occasional common snakehead (Channa striata), red-headed cichlid (Vieja synspilum), and Midas / thick lip cichlids. I have also seen Loricarid sucker catfish there. In the old days there were lots of feeder fish (guppies, mosquito fish, mollies etc) but they have almost all disappeared into the mouths of the guapotes.
As far as i can tell the only native fish there are the baung and the snakeheads but i have only ever caught 1 snakehead there, they are so rare.
The African catfish can grow to over a metre long after about 10 years but such big fish are uncommon though not unheard of, and the usual size is 30-50cm. They look like local keli but usually have a mottled skin pattern and also have a granular texture on the top of the head. I have so far not seen any baby catfishes of this species in the Pandan canal but the adults are quite regularly caught by cast netters and crab bait fishermen so i suspect they are breeding there.
By far the commonest fish is the jaguar guapote which is highly predatory and eats up the fry of all the other species, which may be why they are decreasing in quantity. I normally advocate and practice catch and release, but i consider the guapote such a pest that i always kill it and use it as cat food.
The canal is also dragged by long netters which doesn't help. However the lower section near West Coast road/Pandan Reservoir is now a NO FISHING zone, so it might provide some respite for the fish stocks.
You can fish for jaguar guapote using earthworm (probably best), insects, small fish dead or alive (like feeder mollie / ikan billis size), or pieces of fish meat including jaguar guapote meat. They also bite at night. Mustad circle hooks (not the thick black ones, but the silver thinner wire ones, size 1/0 - 3/0) with the barbs crimped flat work well for this species, which usually hooks itself on them from the drag of the float or sinker.
They will also take flies (including sabiki type tamban flies) and small lures but use strong tackle if using lures as you will often snag discarded long nets or other rubbish. The best time to fish is on dry days. If it rains the canal turns very muddy and the fish don't bite.
Carp including koi used to be quite common but are now rare, usual bait for those is bread. Suggest you release all carp caught. They were introduced by Buddhist Vesak day releasers.