I live in San Antonio Texas and it is very hot and my fish tank is nearing 78 degrees and my big ciclid just died from a horrorendous ick infestation that covered his eyes and mouth, suffocating him or whatever caused his death. So im about to flout my frozen water bottle in the tank and was just wondering, could it cause some form of shock from the cold radiating from it to the fish or do you think it will be ok as a temp decreasing device?