How harmful is soap, cleaning products, etc. to fish?

Question
This book I have called "Pets for Kids" says this: when people started keeping fish, they rinsed their tanks out with soap, and their fish died, soap is very harmful to fish, and that not event he tiniest bit of soap should touch the tank.

Even before you touch the tank, you should rinse you hand very carefully, for there could be some soap from the last time you washed.

A pet store employee also gave me a care guide which was developed and approved by PETSMART vets and it says "always wash your hands before handling fish or cleaning the tank.

My bathtub curtain has white stuff on it, either from dry water or dry soap residue, or both.  I use a bucket to clean my tank.  I am careful not to let the curtain touch the bucket when I put it in the bathtub to clean it after I clean the tank.

In the sink after I wash my hands with soap I have to wipe the water from the sides of the sink with a rag.  When I think I see  tiny soap suds I run water on my finger then wipe the soap suds off with my finger.  

This makes me wonder about other things too.  In the bathroom when I wipe the counter, the rag is hanging on a pipe.  I have cleaning products like a window cleaner and a shower cleaner bottle.  What if the rag gets on the tip of the bottles where the products sprays out of?

My mom uses mustard oil or Canola oil to cook.  She wipes the oil from the bottles with a towel that we have hung on the oven handle.  We also have a towel hung on the handle of our fridge.  I hope to myself that she doesn't wipe those bottles with that towel.  I have told her not to wipe them like that.  I didn't tell her about the fish because I don't think she'll believe it.

If I accidentally mark my hand with a pen I wash it off with soap.  I won't pick up any change I see on the ground outside because I wonder if any oil from a car or anything harmful will be on it and hurt my fish.

Do I have to be that worried about everything?  Thanks.  

Answer
Hi Dipan;

Soap is very toxic to fish but I don't think you have to worry so much. You are doing fine with just basic washing and rinsing of hands and avoiding using equipment or buckets that have had soap in or on them. Washing hands before touching the tank water and equipment is very important. Just no need to get obsessive about it. You could get carried away and make yourself go nuts over it! Touch whatever you want to all day long, just wash your hands before you touch your fish tank and it's stuff.

If you are concerned about drying your clean hands with a towel that may have some cleaner or anything on it, get some paper towels and use a clean one of those every time. That's what I do. If you prefer to use a cloth towel or rag while you maintain your tank, get your own towel and label it "aquarium use only" with a permanent marker. Launder it before you use it after marking it though. That will rinse away anything harmful, just like when washing your hands.

Most importantly, relax and enjoy your fish!

At Your Service;
Chris Robbins