You are right and wrong. Generally there are two media for the filtering system, mechanical and biological.
For mechanical, those brush will last a very long time so one off purchase, if I remember correctly I bought mine at Rm12 per pcs and approx 40 of it in my brush chamber.

For biological media, I use aquaclay if i spelled it correctly but you can opt for cheaper option eg crystal bio, siporax, ceramic ring and the like. All works the same. Biological media will last for a very long time as well with periodic cleaning. (back breaking works)

Pump nowadays consume much less juice le ... this world where got free lunch la ...

If only i have your skill and DIY, can save money as hiring the company to build pond and supply filter cost a bomb.

You are right and wrong. Generally there are two media for the filtering system, mechanical and biological.
For mechanical, those brush will last a very long time so one off purchase, if I remember correctly I bought mine at Rm12 per pcs and approx 40 of it in my brush chamber.

For biological media, I use aquaclay if i spelled it correctly but you can opt for cheaper option eg crystal bio, siporax, ceramic ring and the like. All works the same. Biological media will last for a very long time as well with periodic cleaning. (back breaking works)

Pump nowadays consume much less juice le ... this world where got free lunch la ...

which pump would you recommend?

It depends on what is your application is for.

- water featurel, what is the size of the feature wall and the size of the water retention area.
- koi pond, what is the size of the pond or the tonnage.

The main difference of the two is that for water feature, you dont really need a powerful pump unless its a huge water feature facade.
As for koi pond, you have to consider the turn over of the pond water, minimum for koi pond is one cycle per hour and the more cycle turn over the better. You have to look at the design of your koi pond as to where to locate you return pipe so that the flow is evenly distributed.

I am in the midst of renovating my house and wanting to build a fish pond out in my garden area. Want to have water feature to flow down from the wall into the pond. Not sure what is consider a good design and what media / material / equipment needed for all of this

1.5 feet deep is not very deep at all.
Cats may get to your fish and it can be a bit warm for the fish in the afternoon sun.
Mine is 3 feet.

I am just planning to keep some small fish. I have lots of guppies at home. Over 100. Good thing is the pond is shaded so not direct sun light

Are you keeping single strain/albino/single color guppies?

Well I don't know anything about pond and water feature. Doesn't even know how the filter or pump works. I will like a pond about 3 feet wide 1.5 feet deep and 5feet long. A feature wall about 6 feet height. Want to have water following down from the wall into the pond.

I am thinking of building a koi pond inside my house. I heard from MBPJ that there is a rule that the pond should be at least two feet away from the house boundary but I cannot find this rule anywhere. Does anybody know anything about this? Appreciate your help.