Finding compatible discus tank mates

[Lioness]

I've got a 300 litre setup with 7 discus, roughly 4.5 inches, and 25-30 cardinal tetras. Want to introduce some more movement. Considering rummy nose, rainbow fish, corys, or other larger tetras and barbs.

My tank's heavily planted, with more growth and new additions since the picture. I do 50% water changes twice a week, and I've got 2 x 1400l/h canister filters. Open to any suggestions, really.

[coltin]

I'm not convinced you have enough space for more fish, considering the discus will grow significantly. They'll require a substantial amount of room to thrive.

Rummynose tetras could work, but their colours may be subdued due to the white substrate and lack of surface plants, which is a shame. Rainbowfish might be an option, but I'd exercise caution due to the risk of Fish TB – it's crucial to ensure they're disease-free before introducing them to your discus.

As for barbs, many species can be nippy or too boisterous for discus. Ruby barbs might be a suitable choice, but they prefer cooler water, which wouldn't be ideal for your discus. Some Corydoras species could work, but you'd need to find ones that tolerate warmer temperatures. Suckermouth catfish like Peckoltias, Farlowella, and Loricaria sp. would be more suitable for your warmer water conditions.

On a separate note, I've noticed some of your discus appear to have white edges on their tails – if that's the case, it might indicate excess mucous, suggesting there could be an issue with your water quality.

[Lioness]

I think I'll hold off on adding any new fish for now. Can you point out where the white edges are on the discus' tails, that does sound a bit concerning.

[Lioness]

I'd advise against adding more fish, to be honest. Those discus are gonna take up a lot of space when they grow. Rummynose tetras could work, but they won't be as colourful with your substrate and lack of surface plants. Some rainbowfish might be okay, but I'd avoid them with discus due to the risk of Fish TB. A lot of barbs can be nippy or too boisterous for discus, but smaller ones like ruby barbs could be alright if you don't mind the cooler water they prefer. Some Corydoras might do okay, but you'd need to find ones that handle warmer temperatures. Suckermouth catfish like Peckoltias, Farlowella, and Loricaria sp would do better with the warmer water.

[coltin]

I've circled the areas, but I used blue and it's a bit tricky to see.

[Lioness]

I'm pretty sure it's just the lighting playing tricks on us. If you look at the other picture, the discus don't have those white edges, so I think we're good on that front.

[coltin]

The discus appear to be in good health in the new photo, which is reassuring.

Upon examining the new image, I notice what seems to be a blue-green algae buildup on the sand. I'm wondering if this is just an optical illusion due to the lighting, or if there's a need to clean the substrate.

[Lioness]

I had a real struggle with algae and Cyanobacteria in the past, but I've got it mostly under control now. I've been manually removing it as needed. I don't have any recent photos of the tank to share, but I'll try to post a video tomorrow if you're interested in taking a look.

[Ceese]

Your tank looks great, I'm curious - what plants do you have in there? I'm guessing it's a low-tech setup, no CO2? I've been thinking of adding some plants to my pleco tanks, but I'm not sure what can handle the heat.

[Lioness]

To be honest, I'm not entirely sure about the plants, but I do know there's hygrophila and Valisneria in there. I basically just grabbed a bunch of stem plants from my local store and stuck them along the back. The substrate is a bit of a mix - sand at the front, and a combination of sand, gravel, and some leftover stuff from an old tank at the back. I've got a few root tabs scattered around the back for some extra nutrition. We get plenty of natural light in the room, plus the tank lights, so that helps.