Really sorry to hear the losses of your fish and the spending on the chemicals.
I may be a bit wordy but I hope this will help you understand the basic around using chemicals and fish health.
1. Health Like human and any other animals - Fish immune system can be very strong and fight off many sickness/bacteria on its own - The only thing that does the immune system cannot fight off is mostly parasites (Though sometimes they can mitigate them by promoting slime coat). Or some really serious virus/infection.
So how to promote immune system? Just like human, they need: - Good nutrient - Clean and healthy environment (Basically proper filtration and established beneficial bacteria colony in the pond ecosystem) - Stress-free!!!!!
Moving, catching the fish cause seriously stress unless you did it professionally and swiftly. And this kind of stress is a big culprit that actually kill many fish! Even for big fish like koi!! (I have some experience in rearing and selling koi and transporting is a big issue).
2. Chemicals / Medicine Manganate bath is pretty popular and it's so far seem to be effective in treating parasite (And probably the cheapest method). However, giving them bath in smaller tank/containers with proper fish medicine is my much much prefered method (Usually I use medicine from API brand, both general cure and parasite cure would work depending on your purpose and your parasite). ====>>> Why I don't like manganate bath??? --> Manganate is a strong oxidize chemical, even we human use to disinfect wounds and it's super effective at killing microbes or simple organism. So basically you are dipping the whole fish in a oxidization solution and hoping that the oxidization process kill off all parasites/bacteria (simple organism) before it gets to your fish tissue. Long bath is not good at all and cause serious stress, basically just imagine you have manganate in your organs.
Other proper fish medicine instead of using oxidization, actually use proper chemicals that kill off the targeted parasite/bacteria. Without causing problem to the fish.
Now back to the method you are doing. - M Fluke kill flukes but it also kill the beneficial bacteria that convert Ammonia to Nitrate. You can google "Nitrogen Cycle" if you don't know what I mean.
- M fluke is a chemical, most chemicals do not react to UV light so turning off does not affect the effectiveness of the chemical. Also I think you should have UV light on as UV light can kill parasite/bacteria.
- Parasites may and may not kill fish. They usually kill fish when they reproduce so fast that they overtake vital organs such as gills, guts,..... Or they cause open wounds that later get infected (Fish with strong immune system don't get infected that easily though). So unless you found parasites in the gills of your dead fish (or guts or open wound) then I doubt parasite is the culprit.
My suspicion would be constant water changes + catching and bathing that cause water shock and stress the fish.
Do you know what is the parasite you saw? Its very hard to treat parasite in a 6000l pond just by adding chemicals. Also chemicals that kill parasites will also kill beneficial bacteria --> Ammonia spikes.
My suggestion - Test ammonia again (It's likely to be high now) - Anything higher than 0.5ppm is no good. => If ammonia is high then do water change -> Go buy some bacteria products (It might be expensive in your area) or Go find someone with established filter and ask for some media.
Identify the parasite you saw -> Also see if parasite exists in recently dead fish.
Increase water movement (basically increase areation in the water) -> I found koi and such species are healthier in flowing water
Re: Discuss never successful bred in community?
@Fishlady: yes yes that's what I meant but I had no idea what it is called :P Anyway I will give it a try. My discus are literally laying eggs weekly now since it's raining season.
@Alysonpeaches: Honestly I don't find them that hard to keep even though I know that they are famous for being picky. I kept my tank basically outdoor and it takes all the rain water. I mostly only do water changes during dry season. The lesson I learned when I first started (I did lost some fish) is that make sure you de-worm them and give them proper treatment to avoid long term healthy issue. And give them a big enough tank because they will grow fast. After those lessons, I never lost any discus again!! (Well I did lost 1 more but it was due to jumping :( ). In my community tank, Cardinal tetra, GBRam casualty number is higher than anything else. Never found out why they died though...
I really believe that as long as you understand, do your homework and be gentle. All fish is fine. The biggest killer of discus is stress I think.
Cement is strong enough if you apply enough of it and know the physics. The wall will also have to be strong enough.
Also if you use cement, understand that cement needs to be "cured" before adding fish or the fish will die!!!!!. Google "Curing Cement" for more details. Why? ---- Simple Explanation: Cement when contact with water will "leak cement" which makes the pH rocket to a toxic level for most aquatic creatures. After in contact with water for a while (4-6 weeks), they got cured and don't do this anymore. But then you need to completely change your water in the pond completely.
Alternatively.... I've never thought about doing this outdoor.... but you can use foam!!!!! Yes! Foam is lighter and comes with many color, you can even paint them. You can attach small rocks to them or woods. Or use dried and crush coconut shell to make it looks natural. Google "Paludarium" or something like that, I forgot I it spell. Most of the time people use foam to build rocky walls that look very realistic but pretty light!!!
And like others have said.... we really need visual image to understand what you said best :)
I've a pair of discus that had been laying egg many many times in my tank but never successful, They always lay egg at the same spot but the furthest they ever got was a bunch of free swimmer swimming around them for 1-2 days and they're all gone.
The tank has only tetras and corydas and 3 or discus (5 in total)
I want to try seeing them raising children but moving them is really a pain as they hide so well and they already have their favorite spot
Is there anyway to help them successfully raise young discus?
In my experience, fish are much more active when there is a good flow and good surface movement. Just make sure your pump is strong enough (in this case your pond is not very big, but since these fish can be messy, I would go even 5000-6000l/h)
Also have a pump output create some surface flow too.
Another posibility could be the fish is sick. Are they still eating well? Is there alot of algae growing from the pond's wall?
It is usually suitable for shrimps only and still small tanks are better suited for experienced hobbysts. Especially since you're placing them near the windows.
Small volume of water means the water (temperature, chemistry,...) change more rapidly which create fluctuation and easily stress the inhabitants. Especially when you place them near the window which will get sunlight/wind and tend to have temperature swing easily throughout the day.
Not to mention small volume means the fish have very limited space to swim in. Also limited oxygen supplies. Usually only very small fish or very inactive creatures are recommended for 30l tank (Mosquito bas, shrimps, one single betta,..) but still only recommended for experienced keepers due to fluctuation I explained before.
Thanks to your picture, I recommend you to get a 45litre tank (usually 45cm long) or 60litre tank is the best usually recommended (60cm long). It will probably the twice the tank you have right now though but trust me it will worth it :) . Fish do tend to behave much more interesting when they have a proper environment.
60l will also contains more volume and allow water to change slower throughout the day.
One more reason why people not recommend tank with direct sunlight is also because of algae growth... basically sunlight is intense and contains a wide variety of spectrum which encourage life to grow rapidly. (It means both algae, moss, plants,....). In a perspective of aquascaping, it creates an ugly tank unless you spend time mantaining it. However in term of ecosystem, and if you have good filtration system of course, it encourage growth of plants and algae which are the fundamental part of any ecosystem. - Be very careful too because too much algae will encourage microbe growth, while usually it is beneficial, too much of it + bad filtration and areation can makes the water poisonous for fish or cause bad smell.
What I recommend: - Get a bigger tank, do a lot of research then get your hands dirty :) or - Get a bigger tank, get the good filtration cycle going, get the right inhabitants and do proper mantainance :) https://www.fishkeeping.co.uk/modules/ ... 1&keywords=fishless+cycle Just in case you don't know how to get a good cycle process going.