Don't treat with Melafix - its not a particularly useful medication at the best of times. You Melon is probably malnourised and has had its fins nipped - the 'cure' is to introduce a couple more Discus and spread the aggression around (assuming your tank is big enough) - only treat the Melon's fin if it gets finrot:
READ THIS:
Discus are relatively big and messy fish, they are a schooling fish (like tetras they should be kept in small groups) but they are also territorial and hierachical. Provided you give them what they need they are pretty hardy.
Give them clean, soft water, and plenty of it. You need to do regular, large water changes - I personally change 70% per week. I think they benefit from having driftwood in the water - it softens the water and also releases certain acids etc. that seem to be important to long term health.
Give them companions - unless you have a true mated pair you should keep at least 5 Discus - you can successfully maintain smaller groups, but having 5 or more makes it easier because it spreads the inevitable battles around. 'Dither' fish such as cardinals can help make them feel less threatened - aggressive, fast moving and / or 'nippy' fish should be avoided.
Give them enough space to let individuals form small territories - I use a 'reverse' fish length stocking rule - at least one foot of tank length for every adult Discus. Again, you can stock more, but it makes long term success and happiness harder. They need open areas to swim - don't overplant your tank.
Give them a high quality varied diet - including frozen bloodworms and high quality granular and flake foods with some vegitable content, although protein levels need to be high. I've had good success with the JBL range of foods + frozen bloodworms twice per week. Clean up leftovers after half an hour unless you have Bristlenose Ancistrus or other fish that will consume it - don't leave excess food to rot.
Don't over-react to percieved symptoms - often Discus (like most other animals) will recover from small injuries and sickness without medication, provided you have met their basic needs.
Did I mention water changes?
Chapter Two
COMMON MALADIES AND REMEDIES
These are general descriptions of the most common diseases you are likely to find. It is not a comprehensive guide, and you should research further if you suspect your fish might be suffering from one of these diseases. Do a Google Search etc., and read all of the instructions on the various potions you may be tempted to use. I will add to / update / amend this list from time-to-time.
White Spot
White Spot or 'Ich' is a protozoan parasite that attaches itself to fish. It is present in water everywhere, and will be in almost all freshwater tanks. The parasite goes through several stages over about 10-15 days (temperature dependant), including a free-swimming stage that can rapidly infect other fish.
What it looks like:
The visible stage of Whitespot looks like grains of salt stuck to the outside of the fish. It can appear anywhere on the fish but often attaches to fins and gill plates.
What causes it:
White Spot is invariably caused by poor water conditions in combination with stress - it is a sign the the fish's immune system is failing, allowing the parasite to take hold. As certain stages of the parasite cannot live in water above 28 degrees, it should be less of a problem in a Discus tank as the water should be already be that warm.
What to do:
As it is often caused by poor water, test the aquarium water to determine if filters etc are operating correctly. Do a large waterchange. Raise the temperature to 30 degrees, but make sure that there is adequate water motion to maintain good oxygen levels in the water (as the temperature of water rises, it holds less and less oxygen) - often you will need to add an airstone.
There are several White Spot remedies available, most of which are organo-toxins that work by killing the free-swimming stage of the parasite. As Whitespot eggs can hatch out over a long period of time, most treatments take at least a week in order to break the lifecycle of the parasite - follow the instructions on the product and DO NOT OVERDOSE.
Fin Rot
Fin Rot is usually a symptom of illness rather than an illness per se, although in some cases it can result from direct bacterial or fungal infection.
What it looks like:
Fin Rot begins at the edge of the fins (or at an injury site) and progresses rapidly toward the fin base. It results in a ragged 'torn' fin edge often with a whitish edge (dying / dead flesh). Once it reaches the base of the fin, the fish will not be able to regrow the fin, and infection may spread into the fishes body.
What causes it:
Fin Rot can be caused by physical injury, poor water conditions, poor diet, general stress, or appear in connection with a primary general systemic infection (usually gut infections). It is most often seen in weakened fish.
What to do:
Because it is a symptom, it is important to identify the likely cause before an appropriate treatement can begin. Small infections will often heal without further treatemnt if the cause is found and remedied. The most likely causes are poor water or gut infections. Test water parameters and rectify where necessary. Look for signs of gut infections (see below) and if found treat the gut infection with an appropriate drug. If these causes can be ruled out and there is no other obvious cause, or if it progresses very quickly, treat with Furan2.
Gill and Skin Flukes
Flukes are a kind of parasite that attach themselves to specific parts of the fish. Different flukes attach different parts of the body. There is a particular gill fluke that is known to occur only in Discus gills, and is responsible for the death of many juvenile fish. Most adult Discus tolerate small numbers of flukes without bother - young and weakened fish may succumb to outbreaks.
What it looks like:
Skin and Gill Flukes are usually invisible to the naked eye, but the behaviour of the fish can indicate an infection. Fish that 'flash' or 'strike' objects in the tank may be irritated by skin flukes - those that breathe heavily through one gill whilst clamping the other shut may have gill flukes.
What causes it:
Flukes are parasites that can be carried by Adult fish with little effect. Adult fish can usually suppress any outbeak through their own immune system's defences, however young fish, or uninfected fish that are bought into contact with 'carriers' can be overwhelmed before they develop immunity.
What to do:
Check you water parameters. Treat with Fluke Tabs or Trichlorphon, following the manufactures instructions. Most remedies are organo-phosphates, which lose potency rapidly (especially in humid atmospheres), so buy fresh supplies as you need them and don't store them in your fishroom. Read the warning labels - strong doses of organo-phosphates kill certain fish (like elephant fish) instantly.
There are other treatments, however they involve dangerous chemicals and specialist knowledge, and along with the remedies mentioned above can kill other kinds of fish instantly.
'Hex', Hole-in-the-head
Hole-in-the-head is a condition associated with a flagellate infection called Heximita or 'Hex', although there is good evidence that Hole-in-the-head and Hex are two seperate conditions: Hole-in-the-head is more likely the result of mineral definciencies caused by poor diet rather than Hex, although Hex can infest the wounds.
What it looks like:
This is Hole-in-the-head
This IS NOT Hole-in-the-head (Nares Pores / Sensory Pits)
Fish develop small pin-holes around the eyes and head (not to be confused with the fishes Nares Pores which are normal). These grow in size becoming open wounds if not treated, and will eventually kill the fish as it eats into its flesh.
What causes it:
Many keepers used to think that Hole-in-the-head was caused by Hex infections, however it is now generally accepted that Hex infections are a secondary problem bought about by the fish's immune system failing, allowing it to take hold. The root cause is usually dirty water and/or a poor diet.
What to do:
Check your water parameters - do more regular and larger water changes. Treat the secondary Hex infection with Metronidazole, and improve the fish's diet.
