Thrown into hobby need some serious help!

Hey guys, My mum bought me a tropical fish tank from this really dodgy fish shop not long ago it was a 28L tank and had a hell of a lot of fish in it. So please excuse me but I’ve been thrown into this hobby and have only been doing this for two months so im fairly new.
The 28L tank had
2x Juvi Discus
1x Juvi Angel fish
4x white skirt tetra
10x Neon Tetra
1x Dwarf Gourami
2 x platys
4x Guppies

After about a week I had a suspicion that there was way too many fish in the small tank…and I had to do something about it. I even went back to the store and questioned the man for selling me too many fish with his excuse being "your mum wanted it so I gave it to her" **** customer service and a **** man in general by putting fish’s lives in danger but its all for money I guess.
I have since purchased a 4ft 55Gallon (200L) tank which I have planted and placed some rocks and a bunch of timber for the fish to swim in and around.
I have an internal filter which circulates 800L/Hour and an external filter which does 700L/H so overall my water is being cycled 7.5x an hour which is nice.
My water parameters are
PH: 6.6
Nitrate: 0
Nitrite: 0
Ammonia: 0
GH: 0
GK: 0
My Ph does drop a bit every couple days so I have been adding a bit of KH but the KH and GH has not been rising at all so I’m not too sure if this is an issue or how to fix it?

I have been doing a 50% water change every week

I have moved the discus and angel fish into the 4ft tank and was given another 30L tank which I moved the neon’s and platys in.

My biggest issue now is the 4ft tank. Before the cycle was finished one of the discuses died so I was left with one discus and the angel fish.
After the cycle I bought some more fish and had moved the angel and discus over.
Until recently the tank had
1x Juvi discus
1x Juvi angel fish
1x baby Reticulate/yoyo loach
2x baby khuli loaches
2x Scissor tail rasbora + 1x bloodfin tetra (which came with the second-hand tank)
2x Blue rams
4x baby SAE
3x Otocinclus catfish
My original plan was to get 2 more juvi discus so I went into a store and they said everything would be fine. I introduced the two new discus and my other had seemed to of already established himself within the tank and was hunting the two down like crazy! So I took everything out of the tank – put the fish into bags in buckets and rearranged the whole scenery in order to disorientate the discus fish and hopefully mitigate the aggression. This didn’t work at all which lead me to call up a bunch of stores (including the one where I purchased the two new juvies) and everyone said that I should buy another 3 discus. I went back into the store and purchased 2 discus and 10 cardinal tetras as the assistant suggested to get those if not buying another discus. The fighting has completely stopped, and everyone seems happy and are schooling together but my biggest worry is now overcrowding and algae control. I would like to buy some more oto catfish and maybe 2 more sae but I have a worry that this may be too much for my tank?
I’ve been stressing out about fish for a month and a half now as ive had to save up and buy fish and try and make them all as comfortable as possible.
If it helps I have :
20x bunches of plants in my tank (various types which seem to be growing great!)
1x large timber structure in the middle
2x medium timber structures to either side
and 1x (2 in total) timber structure next to each of the medium pieces of timber
I have 7x rocks in my tank (I don’t think they’re anything special but they all came with the tank when I bought it)
I've also attached some photos for a visual aid.

I would also like to add that the discus to the very right now has a small white growth on the top of one of his fins (looks like a pimple) but i can't get a photo because it's quite small and doesnt show very well.

I feel like im loosing myself in stress and an overload of tasks trying to make their home as perfect and comfortable as possible and every step I’ve taken I’ve been given horrible advice. Before anyone suggests getting another tank I honestly can’t afford another tank right now as I’ve spent close to 1500$ within the last month getting this 4ft tank set up.
I’m hoping some of you guys can help me out a bit.

Welcome to the forum! I am sorry that you have had so much trouble, especially from a fish shop that doesn't understand much about the fish they sell. I would advise three deep breaths and some reading (ok, a lot of reading on this site). What I (we) want is a life-long discus hobbyist! You will get much help and suggestions here. Everyone of us have made mistakes along the way.

However, first of all, check the Discus Beginners section and the sticky topics. They have one for setting up your first tank, along with many other helpful topics.

Here is another must watch from Al, the owner of this site.

Hi Mintekk and welcome to simply. You have really been thru the ringer. Frank gave you some good starting points. Also others will make some suggestions to the tank to make it better for discus but lets start with one thing. Can you do more water changes? This is key to keeping healthy discus and will help with any cycling issues.
Pat

Welcome from me as well, hope you have not been put off by a rocky start. Frank and Pat have given you the two most valuable bits of advice: give yourself as much knowledge as possible (so not to be misled by unprofessional retailers) and give your fish as much clean water as you can manage.
I would like to ask how you have been meaduring the water parameters, as 0 nitrate would mean your tank has not cycled and 0 KH and 0 GH would mean it has been filled only with reverse osmosis water. Did you by any chance use test strips rather than liquid ones? I am asking this because test strips are notoriously unreliable, liquid ones are better (although generally nowhere near lab-grade precise). Keep the information coming, well'help to the best of our knowledge.

Hey all!
thanks for your replies, I have not had time to go through the beginner's guide due to work/university work but I will be having a thorough read through tomorrow.

So far I can make room for 2x water changes a week, I'm thinking Wednesdays and Sundays. If I can find time in the future I will try to do Tuesday, Thursday, and Sundays. I'm sure the beginner's guide will tell me the % of water change but for now, I have been doing 50%.

I have just finished doing some tests with liquid droppers following the instructions. My new readings are as follows
PH: 6.2
Ammonia: 0.25
Nitrite: 0
Nitrate 5
GH: 0
KH: 0

What exactly is reverse osmosis water? by that do you mean purified water? I've just been using water straight out of my tap
Would i have to do something special to my water to getr my GH and KH up? I was looking at changing out some of the rocks for maybe limestone as I've heard that can help.

Not sure if this is relevant but one of my Khuli Loaches has died - the other is no where to be found (assume burrowed into substrate as I moved everything looking for him)
And the white growth on my discus has now completely vanished which is awesome!. I will be doing a 50% water change tomorrow as well :)

R/O water means water purified by reverse osmosis, a process that a lot of fishkeepers have to resort because the water out of their taps is very hard, in particular for the purpose of breeding discus. But it seems you have it coming straight out of your tap, bet a few people on the forum will be green with envy, in any case water totally devoid of minerals is not ideal for the long term wellbeing of the fish, they do need some for their metabolism and more so while growing. Carbonates (measured by KH) are also required by the usefull bacteria in the filter, they are also very important as pH buffers. Without them even a small quantity of acids (like carbonic acid derived from CO2 or nitric acid derived from nitrates) can significantly lower the pH of the water. This in turn adversely affects the beneficial bacteria so ammonia is no longer transformed into less toxic substances. I have no idea if the ammonia reading in your tank could be a warning that this may be starting to happen or because you are overfeeding or the other loach is dead and decaying out of sight. I would advise to gradually increase your KH to about 3, still on the low side but ample to prevent any problems. Limestone can work quite slowly. There are a variety of remineralising products on the market that have rapid effect, or you could try to put sachets of oystershell or crushed coral (or even the grit given to egglaying hens - forgive me but I am a country bumpkin) inside the filter. In the mean time feed sparingly and carry on doing water changes as often as you can. Keep us abreast with developments

Thanks Paul for your advice! I went out on sunday and purchased a small bag of crushed coral which i placed into my filter. Since then I've been testing the water daily and have done a 50% water change 3 days later.
I have noticed my PH was sitting at 7 prior to the water change so i took out a hand full of coral, Today it's sitting at about 6.9 so i will wait a couple more days to see if it balances out and if not I'll continue to take out small amounts of coral until my PH is sitting where I need it. The KH and GH is now sitting at 3 nitrate sitting at 0 still and my nitrate sitting at 5. I'll report again in a few days when i do my next water change :)

Sounds good, keep up the good work

So i have now encountered some more problems.

The PH is rising quite high even with my twice a week water changes. I'm finding that it's hitting 7.2-7.6 and my GH is extremely high (around 8-10) even though I've been constantly taking out the crushed corals I bought a couple weeks ago, I'm down to about 1/5 of what I started with. I'm going to head into my LFC tomorrow to get a softening pillow to lower the GH but not too sure what to do about my PH as it will get too low if i take out the corals I bought. Maybe I can see what happens if i take them out completely during my water change tomorrow.

I have also noticed that for the last week one of my Discus has been sitting in the top corner of the tank. He was looking fine and the only symptoms he was showing was sitting in the one spot and not eating much, so I bumped up my temperature to 30 degrees (86F) and I bought some black worms and garlic guard to entice him to eat which he did on the first day but last night he hadn't eaten at all and today he's completely lost his colour (usually a vibrant blue) and looks like he's showing signs of stress but none of the other fish are showing any signs of issues other than occasional itching and fluttering (which i believe is normal if not constant?)

I thought this may be an issue with oxygen within the tank so I added some air stones to the tank to help with gas exchange but there has been no improvement in his behaviour.

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