Unknown Deaths

[Erised]

I know all of you are gonna say, " its the chinese algae eaters" ... and I do suspect this myself, but seeing as my boyfriend loves them that much, I thought I'd ask around to make sure there is nothing else that might be causing it first. So Please try to answer this as you would not knowing they're in there.

Unknown deaths, last 2 weeks: 1 black neon, 1 harlequin rasbora.
Deaths happen over night, hard to tell if there's any wounds because they've turned all white by the morning.
No signs of illness
Water levels:
Ph - 7
Kh - 10
Gh - 10
NO2 - 0.0020
NO3 - 0

39 Gallon:
9 Zebra Danios (8 adult 1 fry)
2 black neons (used to be 5, 2 unknown deaths in the last 3 months, 1 with definate chunck taken out of it)
3 harlequins (will stock up to 7 soon)
5 cardinals
5 ember tetras
3 peppered corries
1 juvenile common plec (got a 75G he can go into)
3 ottos
2 chinese algae eaters

More info can be given when asked.

 

[WILDER]

You have a nitrite reading of 20, both these fish will not tolerate a reading that high,as black neons and harlequins are quite fragile fish, I would recommend you do a water change, has the tank cycled.

 

[Erised]

I asked my boyfriend for the water test results, seeing as we took them about half an hour before posting this ... we probably got the NO2 and NO3 confused then. Whichever one is ok under 50 is the one we had 20 on the other 1 is zero. Tank has been set up and running for about 6 months, the fish were with me for a bit over a year. So yes, it did cycle

Also, we just moved the algae eaters, I'm a 100% certain it was them now, seeing as one of our other harlequins since today is missing its lower fin, had a lovely chunck taken out of him/her They're on their own in a tank now ... untill we wanna stock that tank, they'll have to go then

Thanks

 

[WILDER]

Glad you found the culpit, good luck in your new arrivals.