Need some help with this mystery!?!

[My Fish Frank]

Ok well here's the deal... I have a betta in a small 2L tank (just temporary) and next to him I have a big 40 litre tank which I am starting up as my tropical tank... I just started by getting 3 black widow tetras and in 1 day 2 have died! (1 seems absolutely fine). Every fish I had in that tank has died including a betta :( the water has been tested (fine) and the betta is in the same water frOm the same tap treated with the same conditioner and I have had no problems with him whatsoever!!! The tank has been rinsed (left running for a while then emptied) multiple times, it has had salt water as well as fresh water rinses and has been scrubbed!

What is going on with the big tank????
(40L JEBO tank with filter, heater, gravel, 2 plastic plants, 1 plastic rock cave thing, and [had] 3 angel fish, then 1 betta, then 3 black widow tettras [only one of which is still alive])


Please help before my last tetra dies on me!!!!!!!!!!!!!

[SnowySurface]

Each of your tanks had various problems. I'll just quickly sum them up below. If I'm off the mark a bit, more info would be helpful.

2 Angel fish alone need about 95L and you have 3 angel fish together in 40L. That is no where near enough room for the angel fish. You would need 112L for 3 angle fish to thrive since they get pretty big. That's all I know about angelfish since I only looked up the fish members say can't be in the same tank as bettas. If you do want to try again with angel fish, then you may have to do a bit of research and get a bigger tank.

Tetra are schooling fish so you need 10-12 minimum of them together or stress can kill them. I think some members have gotten away with 5-6, but 3 tetra isn't a large enough school for them to stay healthy. That is probably what happened to 2 of your 3 tetra. They may have been in a healthy tank, but their school wasn't large enough to make them feel safe and stay healthy. The only way to save the tetra you have is to toss in about 9-11 buddies so the remaining tetra can be part of a school of 10-12 fish.

Bettas do just fine on their own, so I have no idea what could have killed a betta in 40L. If your betta also died in the first 48 hours after being placed in the new tank, do you remember how you acclimated him? If you haven't been acclimating the fish, then shock could also be the causes of their deaths.

I hope my advice helps. :)

[Tikibirds]

OR they could of been sick when you bought the fish.

[Laki]

What is the tail type of the betta? I have seen newly acquired betta with double or otherwise heavy tails unable to swim in a giant tank bc of living for months in a small cup or shallow bowl. They need to acclimate gradually to larger tanks. Then filter flow can mess them up.

Or not properly cleaned decorations. THe gravel I bought was SO stinky when I bought it :/ I know some other things are unnecessarily treated.

Are black widow tetras a hybrid? some fish are man-made and cannot survive for very long unless really carefully maintained. (I can think of some mollies, colored kissing gourami's and "neon" fish off the bat)

Anyway, other than that I'm no expert on tanks and specs. Good luck

[My Fish Frank]

Ok here's some more info... None of those 3 types of fish were ever In the tank at the same time and EVERYTHING was cleaned well after each use (had that problem before.
The 3 angels were only very small.. Almost baby ones so they should have been fine at least for a little while (died within 12 hours)

And I'm actually pretty sure my betta died because of the medication I was giving him (melafix) which I have now learnt to be doing more harm than good.

I also have a small amount of aquarium salt in the water