It's a disease called 'whitespot' or 'ich', caused by a parasite called Ichthyophthirius.
Ich is very common in clown loach, especially if the fish are stressed by poor water quality, being in too small a tank, or not having enough company.
It's not hard to cure, but you must make sure you buy a medication that is safe for 'scaleless' fish like your loaches; it'll say on the bottle; some may recommend that you use only a half dose in tanks that contain scaleless fish.
How big is your tank, how long has it been set up, what filtration do you have, how many and how big are your water changes, how many clowns do you have?
Sorry for all the questions, but if we can't get the conditions right for your fish, they'll be very likely to keep on getting the whitespot.
Thank you, we are going to buy medication as requested
my tank size is 30" x 12" and 15" tall
we have a Fluval U3 filter, i know its over rated for my tank but it dose work well from what i see, one thing i have done is take out the biomax stuff from the 3rd stage of filtering, these i don't know what they are like chalk i guess but made the water cloudy we followed them annuals and left the tank for 2 weeks but still cloudy so we took them out and all went gd
we have 3 red torpedoes and 1 intel fish in there still, we did have 5 loaches and were happy until randomly we lost one the other day, the tank has been setup for 5 weeks total but only had fish in for 3 weeks i do a water change every 2 weeks was the plan i changed the water last weekend at changed around 20 to 30% of the water but today i changed around 75 to 80% of the water after i took out the 4 remaining loaches and took out some gravel as my gravel takes up about 2 inches in hight from the bottom is it better to have more or less gravel i don't know
but when i disturb the water it made the water look really cloudy the fish in there now seem happy and fine
now we have temporarily put the loaches into a tinny tinny tank around 8" wide 4" deep and 4" tall i know its way to small for them altho the loaches are only 1" in length themselves that has a basic filter that come with the tank,
since i started to type this we have lost another loach he was worst of them this morning, tomo i shall go out at get the medicine asap, we have stress coat will that help them? so at moment we have 3 loaches left i hope they can service through the night
***EDIT***
I have looks around being in the uk looking in shops is hard but this is the only shop i can look at online here is this product look okay to use it looks okay to me?
http
/www.petsathome.com/shop/love-fish-anti-white-spot-and-parasite-fish-treatment-57284