Need advice regarding quarantine

[Pokishoosh]

Hi everyone,

I'm planning on keeping discus for the first time (though not my first time keeping fish — I've kept tropical community fish for several years, and I've done a lot of research on discus care before getting to this stage). Everything is almost ready, but I have one big question:

I'm planning to bring in 5 juvenile discus, each around 1.5–2 inches, and my only quarantine option is a 50L tank.

Quarantine Tank Setup:

• 50L (bare bottom — possibly with a small amount of gravel to reduce reflection)
• Inside filter with adjustable flow and surface agitation (NEWA brand, fully cycled)
• LED light
• Located in a quiet corner of the room
• No heater yet, but I will get one if I choose to use this QT tank
• Will add some objects for cover
• Not planning to pre-medicate, but I can get meds on short notice
• Will do ~50% daily water changes if I end up using it

The Source of the Discus:

These will be captive-bred discus from a reputable LFS. I’ve bought most of the other fish from them, and they seem healthy so far. The discus I observed were active, responsive, and went after fingers. I also know some employees there have bred and kept discus for years. They're not cheap either (~$50 each), so it might indicate about a better quality stock.

I understand that even healthy-looking discus from a good store can be sick, but I also don’t want to unnecessarily stress them in a small QT.

So… Should I quarentine them in the 50L tank first, or add directly to the main tank?


Main Tank Setup:

• 240L (120×40×50 cm), fully cycled, running for 4 weeks
• Filter: Fluval 407, with airstone
• Substrate: Smooth gravel
• Heater: EHEIM 150W
• Temp: 26–27°C (will increase to 28°C before adding them)
• pH: Above 7.6 (using API freshwater test, I'm assuming it’s stable)
• Ammonia: 0
• Nitrite: 0
• Nitrate: <10
• GH/KH: Unknown (I’ll test if needed)
• Water source: Tap water treated with dechlorinator
• Water changes: 40% twice weekly
• Feeding plan: Tropical Soft Line America sinking sticks, and frozen bloodworms ~2× per week as a treat

Current Livestock (all added gradually over the past 1–3 weeks):

• 10 cardinal tetras
• 6 Amano shrimp (large, molting well)
• 5 bronze corydoras (1 from an older tank)
• 2 assassin snails
• 1 bristlenose pleco (from an older tank)
• 1 glass catfish (I'm aware that they should be kept in groups of 6+, it happened due to past ignorance and unfortunatly I have nothing that I can do about it. It's a long-term resident, 5+ years)

Plants:

• Vallisneria (2, treated with root tabs)
• Anubias
• Java moss

Planned Additions:

• 5 juvenile discus (will bring them in 4+ weeks, after I see that everything is stable and there aren't any diseases)
• 4 Otocinclus (I'm aware of slime-coat issues, I have a plan for them if they ever start making issues)
• Possibly Amazon frogbit

---

To wrap up: My main concern is whether I should quarantine the juvies in a 50L tank,
or place them directly into the main tank. I'd really appreciate hearing your opinions, especially if you have experience with raising discus.

Also, here's a photo of the main tank:


Thanks in advance!
(Also I apologize if I didn't post in the right section, I'm quite new to this forum)

[jeep]

I would definitely run them through QT first. This is when you observe and treat for anything that may arise.

[dspeers]

Gotta wonder why you are limited to a 50L tank, hard to keep stable water parameters with 5 discus, albeit juveniles. I would go with 29 or 30 gal.

[Pokishoosh]

I would definitely run them through QT first. This is when you observe and treat for anything that may arise.

Thank you! Just to confirm — would you still recommend quarantining even if the QT is only 50L (~13 gallons) for five 1.5–2 inch juveniles? I’m a bit concerned the small space might cause stress or risk stunting during that period.

[Pokishoosh]

Gotta wonder why you are limited to a 50L tank, hard to keep stable water parameters with 5 discus, albeit juveniles. I would go with 29 or 30 gal.

I’m aware it’s not ideal, that’s why I’m seeking advice
Unfortunately, the 50L is my only spare tank

[Vanman]

I would do 80-100% water changes daily in the 50L tank.

[dspeers]

Follow the nitrates, may need more than daily assuming you are generously feeding to prevent stunting.

[Johanna]

Discus that small should preferably be grown out in a bare bottom tank anyway, before introducing them to a community tank with substrate, plants and other fish. That kind of setup has a high bacterial count due to a lot of organic matter which is harmful for young discus' growth. Small discus need to be fed 4-6 times a day with a varied diet and daily water changes, or they will not grow well. so I'd reconsider the size of the discus you are getting if this planned set up is your only possible solution. 240 liters would be a good grow out tank and on the smaller side for a group of 5 adults especially with other fish, If I were you I'd consider emptying that just for the discus and it should do.

[Pokishoosh]

Thank you for your reply — it’s really helpful and informative.
I was aware that bare-bottom tanks help reduce the uncleaned uneaten food levels, but I hadn’t considered that the higher bacterial loads in planted tanks can be harmful to young discus, so I appreciate you pointing that out.
Originally, I aimed to set up a stable tank before adding the discus to avoid problems later on and assumed that it can be manageable, but I now see how that might actually cause some issues.

In regarding to feeding, most sources I’ve read recommend feeding discus 3–4 times a day, but I can increase the feeding frequency, get a greater variety of frozen foods, and do more frequent water changes accordingly.
Also, I understand that 240L isn’t ideal in the long term, but it’s the largest tank I could get, and I can’t dedicate it solely to discus (removing everything else isn’t an option for me). However, I will aim for larger discus (around 3 to 3.5 inches).

Would it still be okay to quarantine discus of that size in a 50L tank, assuming they show no signs of illness? Or given the size of the fish and tank, would it be better to skip quarantine altogether?

[Vanman]

Others will chime in soon, but skipping quarantine is never a good idea.

[Johanna]

The thing is, in my experience (and many others that I know of), discus just don't do well with compromises. If you want to keep discus, they set the rules, or they will get poorly and die. 3-3,5 inch discus are still very young and growing - if they are good specimens -- otherwise they are stunted... so should be treated as grow-outs. I've never attempted anything like it but I doubt they would grow well enough in a 50 liter tank or even do well enough for a qt period of ~6 weeks there, and they likely won't grow very well in a community tank either. If I were you and had just those two tanks available, I'd get a few adult discus around 4,5-5 inches or bigger, and before introducing them, I'd swap all the other fish into the 50 liter tank for the time being and re-start the 240 liter as a barebottom. Then you can quarantine your discus there, do any treatments if necessary in both tanks, and after a couple of months introduce the community fish back in with the discus. After some time, if everything goes smoothly, you could re-scape it and add plants.

[Pokishoosh]

I see, sorry for the late response
it could be possible to transfer the substrate, moss, and Vallisneria,
but I may need to keep the log in the main tank, it might not fit in the 50L (and the Anubias is already well-glued to it, so I won't be able to remove it entirely for the time being).

Also, would it be okay to leave the back layer of gravel along with the Vallisneria plants (using an aquarium safe L-shaped divider to prevent the gravel from spreading, like in the image I attached)? I’m concerned that exposing the root tabs to the water will cause problems like an ammonia spike so I prefer, and I’m not sure if the plants will survive the process well.

In addition, would it be alright to keep the corys in the main tank (after the discus quarantining period)? I’m worried about overstocking the 50L too much for too long.

Last questions,
So is it absolutely not recommended to qurantine the discus in the 50L and then put them in a planted & substrate tank?
and what’s the approximate discus size (or age) when it would be okay to move everything back to the main tank to how it was? even a rough estimate could help.
And thanks again for all the help