More fish deaths

My tank 30 gallon tank had one female betta, seven lambchop rasboras and four peppered cories.

Yesterday one of the rasboras died. They have been dying one by one since I got them, but there have never been any signs of disease or poor water quality. I assumed it was just bad genetics or something.

At around the same time my betta started looking unwell. This morning she mostly stayed pressed against the filter and was really bloated. Her scales didn't seem to be pine coning and she could swim up and down through the water, but she was leaning to the side and staying near the surface gulping air.
I assumed it was constipation and was going to get some stuff to help treat it, but this afternoon I found her dead at the bottom of the tank.

The other rasboras all look physically healthy but seem pretty stressed, maybe because they don't have a big enough school?

The cories all look completely unbothered. All four are active and swimming around the bottom of the tank, none are coming up for air so I don't think there's anything wrong with the oxygen levels.
The only problem the tank has is an excess of algea.

At the moment my only plan is to give away the remaining rasboras to someone who can keep them in a bigger school (I'm not going to buy more just for them to die in my tank), keep the cories and completely clean and re-do my current tank.

Does anyone have any ideas about what's happening or what my options are going forward?

 

Hope I can help, can you answer these questions for me first?

How quickly did they die after you got them?
Where are you getting your fish?
How much are you feeding?
How often are you feeding?
Water changes? How much and how often?
What are you feeding?
Ammonia
Nitrite
Nitrate
Temp
pH
What are you using to test your water?

 

I'm going through something similar with the kubotai rasbora I have in quarantine right now. They were fine, no symptoms of illness. Then they started dying off slowly. I've spent countless hours reading up about possibilities. My water parameters are perfect & I do my requisite water changes. So, that lead me to believe that I am dealing with a possible water quality issue in regards to filtration, not regarding parameters. I honestly believe that I have inadequate filtration and inadequate aeration. I don't have the financial resources right now to purchase more filtration & wave makers. But, Christmas is right around the corner. I'm hoping my suspicions are correct and once I get my water quality issue under control, my remaining fish will do well. If you get the chance, check out that website, especially the articles under fish diseases. That might lead you to the root of your fish death problem. I hope so. Good luck!

 

How quickly did they die after you got them? The tanks been running with fish for 9 months-ish. The rasboras started dying off after a month or two. The betta would've been in there for about six months.

Where are you getting your fish?
Local fish shop - all the fish there look healthy and the water looks clean

How much are you feeding?
A pinch of flake food (don't know the brand), betta pellets (one of the fancier brands, a small amount, maybe 16 1mm wide pellets) and sinking pellets for the cories.

How often are you feeding?
Once a day. I think I was feeding the betta too much though, she was looking a bit fat for a while.

Water changes? How much and how often?
Every two months (not ideal I know but the parameters always seem fine before and after)
Maybe about 30 - 45% each time

What are you feeding?
Same as above, though every month or so I'd collect some mosquitoe larvae for them

Ammonia
0
Nitrite
0
Nitrate
0
Temp
26 degrees Celsius
pH
6.5 - 7
What are you using to test your water?
API test kits


I did try adding an apple snail to the tank recently to help with some of the algea, but he died within a few days. (I bought him from a different shop, it turns out all the snails there have calcium deficiencies)

 

My filtration seems to be fine...
The only other thing I can think of is low oxygenation which could be killing off the rasboras since my other fish can get supplementary air? I wonder if there's a test for dissolved oxygen?
Maybe I'll look into getting an airstone for them or something...
Thanks for the website recommendation!

 

SeaChem Kanaplex worked like magic last tome my tank got some mysterious unidentified disease. In my experience you don't need to mix it with fish food and make the fish eat it wich is what some people say to do. I just put it in the water following dosage instructions.

 

Thanks, I'll have a look into that.

 

How quickly did they die after you got them? The tanks been running with fish for 9 months-ish. The rasboras started dying off after a month or two. The betta would've been in there for about six months.

Where are you getting your fish?
Local fish shop - all the fish there look healthy and the water looks clean

How much are you feeding?
A pinch of flake food (don't know the brand), betta pellets (one of the fancier brands, a small amount, maybe 16 1mm wide pellets) and sinking pellets for the cories.

How often are you feeding?
Once a day. I think I was feeding the betta too much though, she was looking a bit fat for a while.

Water changes? How much and how often?
Every two months (not ideal I know but the parameters always seem fine before and after)
Maybe about 30 - 45% each time

What are you feeding?
Same as above, though every month or so I'd collect some mosquitoe larvae for them

Ammonia
0
Nitrite
0
Nitrate
0
Temp
26 degrees Celsius
pH
6.5 - 7
What are you using to test your water?
API test kits


I did try adding an apple snail to the tank recently to help with some of the algea, but he died within a few days. (I bought him from a different shop, it turns out all the snails there have calcium deficiencies)

Those parameters aren't making any sense. Is this tank planted? You don't have one drop of nitrate after 60 days straight of no water changes. That is very weird, especially for a small tank like a 30 gallons. Fluctuations should be present ... at least nitrate

 

Bubble I am in agreement with SinisterCiclids .
Its just not possible to have zero nitrates and zero ammonia after 60 days of no water changes . Particularly in a 30 gallon 9 month old tank .
Something is wrong with how you are testing the water.

 

Bubble I am in agreement with SinisterCiclids .
Its just not possible to have zero nitrates and zero ammonia after 60 days of no water changes . Particularly in a 30 gallon 9 month old tank .
Something is wrong with how you are testing the water.

Yeah if you are using an API test kit. You might need to shake up those bottles before using and check the expiration date. Or bring your water to a LFS and let them test it and see what they say. Starting to believe that the problem might be an ammonia or nitrate spike.

 

Yeah I thought something was weird as well, took them to my LFS and they came back the same, 0 of everything.
None of the fish have shown any signs of ammonia poisoning or any kind of sickness at all, other than the betta.
Are lambchop (espei) rasboras particularly sensitive to bad water compared to corys?
It seems unlikely that there's something wrong with the tests at both my house and the LFS but it's the best theory I've got so far, the only thing that's confusing me is that the corys have had no issues.