I have lost 4 fish in the last few days. Fist I found a dead guppie female, with no signs of sickness or nipping, or anything at all, dead on the gravel, the next day, I found a male guppie with almost no tail left stuck to the filter stalk thingy, then I noticed that a second male, was swimming around with very little tail left, just a small fork shaped end, he died yesterday, 24hours after I first found him, and then today I noticed my betta (who has been in the tank with the guppies for ages, and never nipped or even went near them) dead in the long grass plants I have up the back of the tank, he also has no signs of sickness or fighting. I assume the two males fought with each other over a pregnant female in the tank, but i can not explain the betta or the first female found. I have two Bristlenoses in the tank, and they are fine, and the rest of the guppies, 2 males 5 females, seem to be doing great. I have done water tests every 2 days for the last 4 weeks, since setting up this tank, and nothing has been out of the ordinary, The ammonia is never out of the first colour range on the API test kit colour chart, same with the nitrate, and nitrite, and the ph is good. The temp varies a bit, (warm house) average is around 26, but i have seen it up as high as 28, and as low as 25. I am sort of stuck, I would like to add some more fish to the tank, to replace those I have lost, and stock it a bit more now its almost fully cycled, but, if i am going to be loosing fish like this, I don't want to right now. Tank is a ar620t 130l by the way. If anyone has any idea's, or any tests i can do other than what I have done, id be grateful for any help to get to the bottom of this issue. I guess its possible its a coincidence, but it doesn't sit right with me to be honest.
I was so sad to see my betta dead. He has been an awesome fish, and was my first tropical fish, so fancy and pretty. I don't think i will find another "Simon the Siamese"