I had been using an Ion rashguard, since first use, it makes a bad smell 1-2 hours after washing it with soap, or not washing it.

Looked it up, smell is caused by a kind of bacteria in sea which likes to grow between polyester fibers. You need to keep it in cold vinegar for about an hour to kill them, then rinse with cold fresh water.

Interesting thing is, my swimming shorts which are olso made of polyester doesn't smell after washing. So i am guessing they like stretchy polyester more.

Are there any antibacterial rashguards available?
Or any solutions to use?

Can't wait to read replies, shirt vs shorts

Does it smell fishy ?

Ditch the polyester. Cotton T's do a good job ??

No it doesn't smell fishy, has a unique smell, similar to the smell when you forget your clothes in washing machine for a day but less disgusting.

Never seen a long sleeve cotton rashguard, wonder why, maybe;
Cotton absorbs huge amount of water so it will get heavy and reduce your buoyancy. They would be significantly less durable and get out of shape quickly after several uses. They are not as stretchy, so when wet fabric sticks to your skin, it may reduce your movement freedom.

When you say washing it with soap do you mean literally? Hand wash? Should be able to just throw it in a cold or warm wash with few troubles. And if still smelly just embrace the funk. It may be your pheromones. You may suddenly attract (more) females?

Yes, hand wash with soap and some shampoo because i wash it when i take shower.

To be honest, its much better when i wash it in washing machine with long program, but I don't have that option everyday.

Hehe, Its not so bad, once you are in the water smell goes away anyway, its just when first wearing it before sessions. I think my feromones attract female bacteria more :)