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jackleroy 02-18-2020 05:31 PM

Lost Harlequin Rasboras
Hi everyone,

I've woken up to two dead Harlequin Rasbora's over the past week and I don't know why. I have a 55 gallon tank with a Marineland C360 filter. The tank also has 8 Scissortail Rasbora's and a pleco. I started with 10 Harlequins and the dead ones weren't eaten or attacked. I'm feeding them Aqueon flakes and my water quality results are below. Any help would be greatly appreciated!

Ammonia <.25 ppm
Nitrate 20ppm
Nitrite 0ppm
pH 7.5
KH 40
GH 30

libertybelle 02-18-2020 09:45 PM

Well the ammonia should be at 0 so it could be cause or effect. It could be the tail end of an ammonia spike or mini cycle which would explain the deaths.

It could also be that you tested right after finding a dead fish in the tank and that itself caused a transient increase in ammonia.

That said in a well established tank even a dead fish won’t cause an ammonia problem for a while. I have tested when finding a dead fish before and still seen zero so it is something to look out for.

Were either the dead or the remaining fish showing any signs of stress or illness? Spots, red gills, red streaks, excessively heavy breathing etc?

How long have all the inhabitants been in there and how long has the tank been running.

jackleroy 02-18-2020 10:27 PM

The tank has been running since November. I cycled it and started adding fish in January, which is when I got the Harlequins. I monitor it very carefully and take ammonia every few days since its still relatively new. It may very well be 0, actually. The color just doesn't look exactly like the vibrant yellow in the testing chart to me. It also hasn't changed in a very long time. None of the other fish are showing any signs of stress or disease at all. Would the KH or GH have any effect on them?

libertybelle 02-18-2020 11:50 PM

Not as long as it’s stable. I kept harlequins in gh/kh of one for years and they bred for me! A couple even survived in the community tank somehow!

Are you testing after a water change? If there are chloramines in your water and can cause a slight ammonia reading that will go away quickly and isn’t anything to worry about.

Both at night? Could oxygenation be a problem at night (sometimes happens if you have live plants) if you look into the tank right before lights on are the fish at the surface?

jackleroy 02-19-2020 12:04 AM

One of the Harlequins was at the surface a day before he died. Oxygenation was my first thought and I installed a bubble bar that day before I went to bed. Is an 18 inch bar enough to keep the tank oxygenated in between monthly water changes? I'm new to cannister filters and used to a hang on the back filter providing some some oxygen.

Breeding Harlequins must have been fun!

libertybelle 02-19-2020 12:21 AM

I don’t think size makes too much difference as long as it’s moving the surface about. An 18 inch bounce bar should more than cover that possibility.

It was a total accident and all I contributed was clean water and tons of plants!; I did zero conditioning, the first time they spawned in quarantine and I was about to drain the tank when I saw them. The second time I’m doing a head count and there’s another tiny one right there in the community. And yes; they were utterly adorable.

Unfortunately as to your problem if there’s no symptoms it’s really hard to say what might be wrong. Not to sound defeatist, but sometimes you do just lose fish in the weeks after they’re added just because they’ve been through a lot and you don’t really know why. Hopefully it’s just stress catching up with a couple of them and the rest will be fine!

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