Fish are dropping dead & I don't understand why

scotchegg

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Hi everyone, I'll try and be as thorough as possible about my tank, but to start with, about a week ago my firemouth mysteriously dropped dead one day, despite me not once noticing anything wrong with him. A week on and I've since had a GBR and today, my angelfish die suddenly too. The ram did get a swollen stomach the day before dying, the firemouth and angelfish showed no outward signs of issues.

Aquarium is 120 litre planted with some wood and rock, under-stocked before, definitely under-stocked now.
Water params are totally fine, tested with the API liquid kit and strips for good measure, 0 Ammonia, 0 Nitrate, 20-40ppm Nitrite (this is how my water comes from the tap, I have Seachem matrix in one of my filter baskets but that does nothing to help).
I treat my tank with Fluval Aqua Plus water conditioner when I do water changes (weekly, 30%), along with adding the correct dosage of Seachem Pristine.
I feed the fish once a day with a random choice of one of either tetramin flakes, hikari micro wafers or new life spectrum pellets and bloodworms once per week.

I really have no idea what's going on. I've had the tank running about 6-7 months with no issues, everything peaceful and no chasing or fighting amongst the fish. the two GBR would occasionally pair up and occasionally decide they hated each other now and then, but mostly they just kept themselves to themselves. Now there is just the single GBR left with 8 Black Phantom Tetra and a plec, the tetra and the plec seem fine to me, but I have seen the GBR rub on a piece of wood a couple of times today, which isn't normal but I don't know what that means.

Aside from that, the tank has had an ongoing issue for about 5 months with blue green algae, though I treat any larger outbreaks with Blue-Exit and mostly keep on top of it by physically removing it on every water change which has kept it at levels where you honestly wouldn't notice it. It does occasionally run rampant over my moss very quickly, at which point I physically remove it with my gravel vac.

So right now it's a total mystery, does anything I've said ring any alarm bells to you? Any input greatly appreciated because right now my fish are dying, which sucks but I have no idea what I'm supposed to do to stop it and no motivation to restock because I don't want to get healthy new fish only to have them die. If you need any more info, I can provide it.
 

Gel0city

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I think all your fish do not have the appropriate space to live in. Prior to the deaths, you said there were 2 GBR, firemouth, angelfish, 8 Black Phantom Tetras, and a pleco. Since I use gallons, 120L = about 30 gallons. You need a bigger tank for your pleco and all your other fish, since plecos can grow at least 6 inches. Instead of GBR, you could go for one school of tetras, or a few angelfish.

Edit: I think aggression was the main cause of the deaths. Aggression led to constant stress, which killed some of the fish, but I have no idea on the swollen belly.
 
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scotchegg

scotchegg

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The fish were not being aggressive, trust me I watch them every day of my life. They were also all pretty small, I forgot to point out I didn't add them all on day 1, the tetra were basically fully grown as they were my first fish, but the plec is about 2-3" right now as I added him last, maybe 3 months ago? The firemouth was the biggest fish in the tank at about 3-4".

I checked my stocks using the online stocking calculator and it showed me using something daft like 70%-ish of my filtration and stocking capacity. I also had three separate territories set up on the far left, right and centre of the tank because I was always aware that the GBRs and the Firemouth might have issues. The angelfish was the most placid fish going, he would swim around casually with the Firemouth. In fact, the fish that have the most agg is the tetras, who like to flare up their fins at one another for some handbags pretty much daily before they get bored and go back to ignoring one another.
 

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Do you know your water pH? Low pH can lead to pH crashes and such. Did you recently add any fish to your aquarium, and how many? Did you remove any of your tank's sponge/filter (could remove or harm BB) As for the pleco, he will eventually grow larger. Plecos are a huge poop machine and require lots of water changes and filtration. Do you know what species/type your pleco is?
 
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scotchegg

scotchegg

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Oh yeah, sorry, she's nothing special, just a standard bristlenose (assume she's a she, since she hasn't really got the bristles).

I haven't tested for PH with the liquid test kit for a long time to be perfectly honest, though I would check occasionally with strips. Checking it now, it appears to be pretty solid on 7.5
 

Gel0city

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Test strips are pretty unreliable compared to the API Master Test Kit. You can do some research on that if you would like. I would suggest getting API Kit and then retest your water, as there could be a major difference. Standard bristlenose grow up to 4 inches about, which is fine for your tank. Keep up on your water changes and gravel vacs (if you have gravel substrate) since plecos are a HUGE waste machine.
 

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