Sick minnow+danio+guppy?

[Ami_bby]

About a few weeks ago I had bought a 21gal tank and I had a 4gal tank with a minnow and a danio (all the others died off). I had only bought this bigger tank because I wanted to give them friends so I left the tank for like 4 days with a filter from a cycled tank and live plants.

Then when I went to the pet shop to buy a big piece of wood for the middle I was speaking to the guy and he told me I was fine to put fish in so I bought 4 danios (and he gave me a free one) and I got 2 minnows and he told me I have massively under stocked my tank so I asked him what he would recommend he said guppies.

There was a 6 for £10 sale on girls and 4 for £10 on boys so I got 11 (he gave me a free girl).I properly floated the bags and everything now all my fish look sick and fat.
The single danio has had a bent back like this for a while I have had him for like 3 yrs but the others look really pale and have red gills and eyes are big.

 

[Circus]

Have you tested for Ammonia, Nitrite, or Nitrate?

Red gills Tends to indicate ammonia poisoning. I would do a large water change (75% at least) for now, and do one when you test for any Nitrite or Ammonia as any amount if these is harmful to the fish.

 

[Ami_bby]

I don’t have any more test strips left and can’t go out to get them (I have covid) so I’ll order some and do the water change asap. Thank you.

 

[Colin_T]

Your tank isn't big enough for all those guppies. Take the males or females back and only keep one sex in the tank. The females will have babies without males being present and you will end up with lots more in the near future.

If the fish ever look sick or unwell, do a 75% water change and gravel clean the substrate every day for a week or until the problem is identified.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

 

[Ami_bby]

I will do the water change and gravel cleaning but I have just checked and they don’t take returns. Won’t the fish eat most of the babies anyway? I am planning on buying a used 30gal from a friend and I will have the money for it in 2 weeks. For the time being could I keep the 4 boys in the 4 gal.

 

[Colin_T]

If you are getting another tank soon, then keep them together until you get the new tank. Then take half the water, gravel and filter media from the old tank and use it to set up the new tank. Move the males or females into the new tank and top both tanks up with dechlorinated water.

Reduce feeding for a few weeks and monitor the ammonia and nitrite levels. When the filters have recovered, increase feeding.

 

[Ami_bby]

Ok thank you