What you'll be needing
Quite probably the most asked question when it come to the equipment you need to run a Discus aquarium is "what is the best…" Well that is very subjective and will often be a simple matter of opinion based on experience of particular equipment. You can spend as much money as you have on the latest gizmo, the new technology, but at the end of the day all you have to ensure is that your water is heated and clean.
Here is my take on the subject,
Aquarium
Water will be more stable and less susceptible to temperature and pH variations the more of it you have, so buy the biggest you can afford / fit into your home with a minimum volume of 180 litres in mind.
Today you can buy systemised aquariums, a plain "glass box" and so on. They all do the same thing - hold the water, so select one to suit your circumstances, the actual dimensions are not so important as the total volume of water. That said don't go for too deep or you will not be able to reach the bottom to maintain it.
The volume can be increase by running a sump underneath to house all the equipment, or you can plumb a series of aquariums together to make a "system"
Filter
The filter is the life support part of the aquarium, without one your Discus will die.
The primary function of the filter is "biological" to deal with the ammonia the fish produce, then the nitrite and this in turn becomes nitrate. As water will flow through the filter, it also remove any sediment from the water, it is this that blocks filters and is removed by regular cleaning. A third filtration stage is "chemical" this is where you can add a media or resin to the filter to polish the water, or remove phosphates, nitrates and all manor of other dissolved substances.
A simple air driven sponge will clean the water biologically, also mechanically. Internal electric powered filters do the same. External canister filters and sumps have the additional function of chemical filtration as an option.
Filter bacteria require well oxygenated water to thrive and work, so always get a filter bigger than you think you need. They can all be turned down, but none will work above their maximum capacity.
Filtration in my experience is best kept simple. A guide to how to mature and maintain the filter bacteria can be found here..
Heating
Discus require higher temperature than "normal" tropical fish to thrive. (28-30 C) So to achieve and maintain this you are looking at around 1 watt of heating power per litre of aquarium water.
Don't cut corners with heating and buy the cheapest heater (s) you can find. This really is an area where you get what you pay for. You may have several hundred pounds worth of Discus. Is it worth the risk of cooking them with a faulty stuck on heater for the sake of £30? The answer of course is "no" but people do and horror stories are rife on Facebook for example.
That said a £60 heater is not totally immune from malfunction, but the more developed heaters do have thermal protection and cut outs as standard. It is a very good move to further protect you heaters by linking them up to and external control such as an ATC 300 or STC 800 as these will cut the power and sound alarm if a malfunction occurs. For under £100 you can install a Seneye system, this will monitor the temperature (and pH) of your aquarium and through a server can send messages to your mobile phone and stores a record on line for you to look at.
Lighting
Bit of a myth that Discus don't like "bright lights" but what we need to aim for is lighting that shows off our fish to their best. Not so long ago the best we had available to us was the "Grolux" tubes, these really extenuated the red and blues in the fish. And folk like me still use them, but they are not economical to run. So the modern way is to use LED lighting, very low wattage and available in a rather daunting combinations of colours.
Before committing to LED lights it really is of benefit to talk to people who have them, and again it is an area of the hobby where you do get what you pay for. The difference between a £10 light on Ebay and a £200 Kessil Sun might not be immediately obvious, but after a couple of weeks it will. Buy the best you can afford. We spend hundreds on our fish, so it makes sense to invest in a good lighting system to see them at their best.
There are of course dozens to choose from, some have 5 year warranties, which is very good and gives you complete peace of mind. You can also buy remote controls, controls that work over the Internet, via a smart phone, some have computerised timers that will simulate sun rise, sun fall and even thunder storms.
Night light. If you have none or very little natural daylight in the room it is advisable to provide the tank with a small night light, a moon light tube or just a light in the room. The reason being that Discus do appear to sleep during complete darkness, but they are also easily spooked and will dash around the aquarium frantically. This should be and is easily avoided.
Air Pump
I run extra air into all my aquariums. Some folk will argue that the return of the water from the filter is sufficient for oxygenating the water, but you cannot overdose dissolved oxygen and as we run warm water, which gets even warmer in the summer months adding extra air is like a "shot to nothing" "no risk"
There are other benefits from adding movement from another source, firstly it will help gas off CO2 which will help maintain the pH also should you return pump fail the fish have a source of oxygen. You don't need the airstone to be creating a washing machine scenario in your tank, but a gentle flow of bubbles does no harm at all.
You can use a small single pump or for larger installations create a "ring" and draw the air from this reservoir.
UV Steraliser
Do you really need a UV steriliser?
IMO, there is no doubt at all that these are a benefit to the hobby of keeping Discus. You can't see what they are doing as such, but over you will be aware of less or no algae in the aquarium. The fish recover from minor scratches and split fins very quickly indeed as the UV keeps water born bacteria levels to minimum. And if you breed Discus you will notice far less fungused eggs.
A UV may not be essential, but they are a very handy tool for the Discus keeper.
Test Kits
If I've heard "my water's spot on" once I heard it a thousand times in response to the question, this is usully followed by "what's the pH" answered by "about 7 to 7.6" .... well it can't be both, the pH is an exact reading and as pH is logarythmic there is a considerable difference between 7 and 7.6
So a prudent fish keeper really should know their basic water parameters and test them regulary.
An ammonia, nitrite, nitrate, pH and KH test kit is a minimum in my opinion, to that you can add a GH, dissolved oxygen and phosphate kit if you feel the need.
pH and TDS are also monitored easily with affordable electronic devices.
The point is deteriorating or slightly off water conitions will be the early waring sign that somethong is wrong and the fish could get ill, so it really is in our best interests to know what our water parameters are and if you like keep a log to see any patterns that develop.
Do not rely on your local fish shop to test your water, by the time you have decided it needs testing will often be too late.
Anything Else
Well that's all the basics that will keep your Discus alive. You will accumulate many odds and ends like hoses, nets and items that seemed like a good idea at the time but remain in their box.
It is a good idea to have a selection of spare parts, an air pump, a heater and so on. I'm often asked and see the question on the Internet a lot, people ask "what medications do I need as a first aid kit?" Well it is a good idea to have some cooking salt, maybe an antibacterial treatment etc in a cupboard, but if your water is good, your fish are genetically sound, fed well and so on the chances of ever needing them are minimal.
Water preparation is very important to the long term health of any fish, and I have a dedicated article on how we do it, and why Here...