Looks like white spots. Are your cardinal tetras opening and shuting their mouths? If yes, it is most definitely white spot. Also try to spot diferent swimming patterns and rubbing their gills on gravel. Those are common symptons of ICH (white spots)
since your fish already have the white spots then you shoud do a 80% water change and clean the gravel and filters once thats done raise the temperature to 30°C and leave it for a week to kill the new born parasites. After waiting a week do a 75% water change. If you want you can put all the infected fish in a QT and put some medicine in the water. But remember to clean the main tank as it is already infected and it will spread rather quickly.
As said before, raise the temperature in your aquarium as this stops the ich from reproducing. Make sure you do this gradually, only raising it by 1 or 2F each day or else your fish will become stressed. Get aquarium salt too.
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Would washing the sand with warm water be enough? I have found some anti white spot from internet but it says not to use with scaleless fish so I think I will remove the cardinals from the fish tank and treat them instead of the whole aquarium. I will do the water changes too as advised.
hello Colin, thank you for your message. As I understand, I may not need to use the anti-white spot if I do a huge change of water, clean up of the sand, and temperature increase. Is this correct? Also, could you please advise me on the best way to clean the sand? Thank you!Good old white spot.
Do the huge water change and gravel clean. Clean filter. Raise temperature to 30C/ 86F and keep it there for 2 weeks or at least 1 week after all the spots have gone.
The Corydoras should be fine with the heat.
Increase aeration/ surface turbulence to maximise oxygen levels in the water.
The following link has information about white spot including its life cycle and different ways to treat it. Post #1 and post #16 are worth a read.
What is ICH?
WHAT IS ICH? Ich or Whitespot is a parasitic protozoan that infects fresh, brackish and saltwater fishes. It is identified by small white spots that appear on the fish's body & fins. There are several stages to this parasite's lifecycle and it must be noted that the parasite can only be killed...
No because your tank is already infected, so you will have to treat the whole tank to eradicate the parasite. If you dont do so the parasite will soon infect all your fish again.
Would the Cory be fine with the internet medication or is it best to isolate them? Thank you
