Hi Stefan... and welcome to the forum. I'm a beginner so I can give you some tips about how to get started... but you'll find plenty of experts here who give great support.
You should do heaps of reading on this forum (using the search tool) before you buy anything or do too much planning. I can't give you tips on discounts in Perth but following are some things worth reading up on or things I wish I'd done differently.
Cycling... I did fishless cycling and it's not as difficult as it first seems - just needs a bit of patience. Read about the various bacteria that convert fish waste to fertiliser.
Grow Bed to fish tank volume ratios. My fish tank is too big for my grow bed. There's a bit of flexibility but wish I'd set up with something closer to a 1:1 ratio.
Get your bell syphon right from the start (if you're doing flood and drain)... mine's too small so I struggle to get enough water through my grow bed. There are plenty of designs in the forum and on the net. They're easy to make or you can buy them.
Stocking ratios. Don't be tempted to buy too many fish... I did and now I'm having to give fish away. it's amazing how few fish can keep so many plants healthy. Again, there are heaps of posts with advice on this.
Choice of fish is important... I started with silver perch which grow a bit slowly but are pretty tough so good for beginners. All of mine are going strong after nearly a year. Some people use goldfish (particularly if you don't want to eat the fish eventually). I know people in Perth are raising barra... but I think they aren't beginners like us.
pH and buffer (alkalinity) management... I took a long time to understand this and I'm still learning. Don't be tempted to buy chemicals from pool shops or pet stores. What you need is in most hardware stores or online. But what I've learned the hard way, is that it's best not to be constantly testing the system and trying to change the pH and buffer - it tends to settle down and find its own level after a while and the fish and plants (and good bacteria) are pretty resilient anyway.
pumps... get one a bit stronger than you think you'll need... you might end up having to add more growbeds and it's always helpful to have some of the extra water flowing straight back into your fish tank... creates water movement and oxygenation
that list is only a start and I'm sure I've left some important things out. But I reckon you've picked a great project...
you'll learn about plant management, fish biology, water hydrology (all about the science of water flow), a little bit of plumbing, water chemistry. It's fun feeding the fish (the silver perch really go off when the pellets hit the water) and the plants taste great.When you've done your reading and worked out a rough design for your system, you should post it here... with a rough diagram or description of how things are connected up, the volumes of your tank and grow beds, the size of the pipes you plan to use, the size of the pump and how many fish you plan to have. You'll find you get some good advice... I'm confident of that, because I did.
Good luck
