need urgent help

[abominus]

i have put four irredescent sharks, four silver dollars and a raphael catfish in a 12 foot pond. they have been in there for 2 days. the problem is that the temperature at night drops and at sunrise it rises.So at night all fish become very lethargic but when sun comes up, It warms up the water so they become active.Now i have noticed that there is some blood on back of my smallest id shark and it is very lethargic and comes up and swims half outside water. The biggest id one has some white patches on its face but it is swimming fine along with other fish. Is there something to worry about.Please reply

 

[A201]

What is the temperature range?
Please provide pics if possible.

 

[abominus]

at day the air temperature is 28 degree cesius and at night the temperature is 17 degree celsius

 

[abominus]

By the way the smallest irredescent shark died. But please tell me what is the problem.

 

[A201]

That's quite a big temperature swing, which might be stressing & weakening your fish to the point of disease.
White patches on a fish can indicate several health issues. The most prevalent would be a bacteral infection ""Columnaris".
Visible blood spotting on a fish can be simply an abrasion or could be Septicemia, which indicates some sort of intestinal infection.
You didn't note the water parameters.

 

[duanes]

With those wide temp swings, species must be chosen very carefully.
That swing is a bit too drastic for any tropical iridescent sharks, and the cats.
It my also be too drastic for the $'s unless you are able to access the southern S American (Uruguayan or Argentinian variants.
The type cats I would have chosen would be north American bullheads, or channel cats
In place of the sharks, more temp swing tolerant species would be north american shinners or Uruguayan tetras, or.....carp.

By the way how deep is the pond?
Water depth has a big influence on water temp stability.

 

[abominus]

5 inch is the depth

 

[jjohnwm]

Surely those numbers are referring to air temps and not water temps? Unless that 12-foot tank is only about a foot deep, I am certain that the water temps are much more moderate at both extremes.

Shading the tank from the heat of the sun would help with the high end, and placing a cover over it on the cooler nights would be beneficial at the low end.

Edited to add: Just saw your last answer. Five inches?!?! You've gotta be kidding. Five inches of water will experience insane temp swings, and will also keep those poor fish in a constant state of sheer terror...both stressors which will lead to disease. Can you not fill up the pond much deeper than that? If that is the max depth you can offer, IMHO, this is completely unsuitable as a home for those large flighty fish.

 

[abominus]

also i have a 300w and 100w heater
both set to 32 degree celsius

 

[A201]

I'm no pond expert, but five inches is much to shallow for an outside pond.
I dug a Koi pond for my parents that was two feet deep. The Koi thrived in it, in a State where summers are extremely hot & winters can be very cold.