Concern in my 75-gallon community tank

[Stefan]

Hey all,

So I've got a 75 gallon tank with a pretty diverse group of fish. There's my red spotted severum, an EBA, a Synodontis catfish, three Rainbows (down from five, sadly), and six polar blue parrot convict cichlids.

I've been doing 40% weekly water changes, and the syno's been doing a great job keeping the nitrate levels in check. The water readings are perfect, but I still lost two Rainbows recently. One had lymphocytis from the start, so I figured that was the cause, but then another one died a few weeks later. I've been observing the tank, and I noticed one of the Rainbows doesn't school with the others. It just hangs out alone, but it doesn't seem lethargic or sick.

I also noticed that when the Rainbows get too close to three of the bigger PB cichlids, they get chased away. It's not aggressive, just a quick nip to keep them at bay. This is new behavior, and I'm wondering if the stress from the PB cichlids might've contributed to the deaths. My theory is that the PB cichlids are stressing out the Rainbows, but they're not actively targeting them.

I'm considering a few options to address this. I could add more tall plants to break up the tank, but I'm not sure that'll make a big difference. I could remove the three larger PB cichlids, but I think the smaller ones might just take their place. I do love the PB cichlids, though. Another option is to rehome the Rainbows and try introducing something new, but I'm not sure what would work well in the tank. I've tried other fish in the past, like rainbow cichlids, acaras, geophagus, and gouramis, but they didn't do well.

I'm also thinking about bringing the Rainbow population back up to five or six to see if that'll help. Maybe I could remove the most aggressive PB cichlid and rearrange the tank to create new sections for the fish. Any thoughts on what I should do?

[coltin]

I would love to see some pics or a video of your tank and the fish. Have you noticed anything unusual about their poop? Are they eating normally? I've heard of some fish getting bloated right before they die, do you notice any changes in their appetite or body shape before it happens? Also, do they tend to hang out near the surface or the filter outlet before passing away? And do you notice any changes in their eating habits before they die?

I'm also a bit concerned about the number of convict cichlids you have in the tank. I know they're beautiful, but they can be super aggressive, especially when they're breeding. I've had some experience with them before and it was a real challenge. Don't get me wrong, I love them, but they do require a lot of space and can be quite territorial. Have you considered rehoming some of them to give the rest of the tank a break?

[willie32]

I'm pretty sure you're not getting zero nitrates every week, what test kit are you using? The Severum might have something to say about a nitrate-free tank, haha.

You mentioned one of the Rainbows had Lymphocytis - are you certain about that? I'm thinking sores on the body could be fish TB, it's pretty common in Rainbows.

@coltin, those Polar Parrot Convicts are hybrids, so they're not as aggressive as the real deal, and they've got that parrot fish mouth, so they can't do much damage.

[Stefan]

I would love to see some pics or a video of your tank and the fish. Have you noticed anything unusual about their poop? Are they eating normally? I've heard of some fish getting bloated right before they die, do you notice any changes in their appetite or body shape before it happens? Also, do they tend to hang out near the surface or the filter outlet before passing away? And do you notice any changes in their eating habits before they die?

I'm also a bit concerned about the number of convict cichlids you have in the tank. I know they're beautiful, but they can be super aggressive, especially when they're breeding. I've had some experience with them before and it was a real challenge. Don't get me wrong, I love them, but they do require a lot of space and can be quite territorial. Have you considered rehoming some of them to give the rest of the tank a break?

I'll post some videos and pictures of the fish later today, I've got a symposium this morning so I'm running a bit behind. The fish seem to be eating well, no issues with their poop that I've noticed. They didn't appear to be getting fat overnight before the last one passed, and they're not hanging out near the surface or filter outlet. The one that's been keeping to himself is usually just mid-level on the side of the tank. They all seemed to be eating fine, but I'll keep a closer eye on them tonight. Also, just to clarify, the PB cichlids are hybrids of convict and parrot fish, not pure convicts.

[coltin]

Don't add anything to the tank just yet, let's figure out what's going on first. The fish in your picture look fine, no signs of Fish TB, that's a relief. I don't think the cichlids stressed out the rainbowfish to death.

I'm having a hard time believing the nitrate level is always 0ppm. Are you sure you're using the test kit correctly? I've had issues with those kits in the past if you don't shake them properly or add the reagents in the right order.

How often do you clean the substrate? Do you dechlorinate the new water before adding it to the tank? Are your buckets and hoses specifically for the fish tank?

What kind of filter are you using? How often do you clean it and what's your cleaning process? What's your feeding schedule like? What do you feed the fish and do the rainbows get any plant matter in their diet?

[Stefan]

I would love to see some pics or a video of your tank and the fish. Have you noticed anything unusual about their poop? Are they eating normally? I've heard of some fish getting bloated right before they die, do you notice any changes in their appetite or body shape before it happens? Also, do they tend to hang out near the surface or the filter outlet before passing away? And do you notice any changes in their eating habits before they die?

I'm also a bit concerned about the number of convict cichlids you have in the tank. I know they're beautiful, but they can be super aggressive, especially when they're breeding. I've had some experience with them before and it was a real challenge. Don't get me wrong, I love them, but they do require a lot of space and can be quite territorial. Have you considered rehoming some of them to give the rest of the tank a break?

I agree I haven’t added anything as of yet hence why I came here first. That picture of the rainbow fish isn’t the one that had lymphocytis but the stock image I put resembles the bump she had on the side of her body for the year I had her.

1) I do follow the proper procedure for the tests - shaking every bottle and adding the reagents in the correct order, 1 then 2.
2) I clean the substrate weekly during my 40% water change.
3) I use Prime water conditioner to dechlorinate any new water added to the tank.
4) I have separate equipment, including a syphon and bucket, for each of my 2 tanks.
5) My filter is an Aquaclear 110 with 2 foam layers and 1 bio layer - I don’t use carbon unless it’s for medication purposes, which hasn’t been necessary in a few years except for a treatment of melafix a few months ago.
6) I clean the filter every 1-2 months using only dechlorinated water or tank water.
7) My feeding schedule is every other day, and I give them a mix of omega cichlid pellets and veggie wafers/pellets - I don’t feed them actual plants, just the veggie-based pellets.

[coltin]

I've always had great results with duckweed in my rainbowfish tanks - the fish just love grazing on it throughout the day, it's a great way to get some plant matter into their diet.

Lymphocystis is usually a sign of stress, and it's pretty rare for it to last as long as a year - I've found that if a fish is really stressed, it'll often succumb to illness during that time, so it's unusual that your rainbowfish managed to hang on for so long. Normally, it'll clear up on its own once the fish has settled in, and it's usually gone within a month or two.

At this point, I think it's a good idea to just keep a close eye on your fish for any signs of aggression or unusual behavior. If you notice anything that doesn't look right, try to film or photograph it and post it here as soon as you can - hopefully, we can work together to figure out what's going on.

[Stefan]

I would love to see some pics or a video of your tank and the fish. Have you noticed anything unusual about their poop? Are they eating normally? I've heard of some fish getting bloated right before they die, do you notice any changes in their appetite or body shape before it happens? Also, do they tend to hang out near the surface or the filter outlet before passing away? And do you notice any changes in their eating habits before they die?

I'm also a bit concerned about the number of convict cichlids you have in the tank. I know they're beautiful, but they can be super aggressive, especially when they're breeding. I've had some experience with them before and it was a real challenge. Don't get me wrong, I love them, but they do require a lot of space and can be quite territorial. Have you considered rehoming some of them to give the rest of the tank a break?

I'm considering adding duckweed to the tank for the rainbows, but I'm worried the severum will destroy it. If it'll benefit the rainbows, I'll definitely look into it. The tank's been pretty much the same as yesterday, not much aggression to report, but the one rainbow is still keeping to himself.

[coltin]

I'm thinking the aggression I noticed was more from the cichlids having a go at the rainbow fish, but it's not like they're actively chasing them down or anything. They just seem to get a bit territorial if the rainbows get too close. Also, I didn't think about this before, but I've been reading that severums need some plant matter in their diet too, so I might need to look into adding some more variety to their food.

[Stefan]

I would love to see some pics or a video of your tank and the fish. Have you noticed anything unusual about their poop? Are they eating normally? I've heard of some fish getting bloated right before they die, do you notice any changes in their appetite or body shape before it happens? Also, do they tend to hang out near the surface or the filter outlet before passing away? And do you notice any changes in their eating habits before they die?

I'm also a bit concerned about the number of convict cichlids you have in the tank. I know they're beautiful, but they can be super aggressive, especially when they're breeding. I've had some experience with them before and it was a real challenge. Don't get me wrong, I love them, but they do require a lot of space and can be quite territorial. Have you considered rehoming some of them to give the rest of the tank a break?

Hey @coltin,

I've been keeping an eye on the tank and I haven't seen anything out of the ordinary, except for that one Rainbowfish still keeping to himself. I did notice he's got some nip marks on his fin, not sure if it's from the PB or one of the other Rainbows.

Those two orange Rainbows are pretty entertaining, they swim side by side and do this little dance thing.

I just took some measurements before my weekly cleaning:

Temp: 75
Ammonia: 0.05
Nitrate: 0
Nitrite: 0

I'll be doing my usual water change today. I'll also set up my phone to record a 10-minute video later, so you can get a better look at the tank's normal behavior.