Are Clown Loaches Sensitive To Excel?

[Amunet]

I had a clown loach die a few days ago for no apparent reason. The day before, I had done the weekly water change, nothing different there, and then added in the plant ferts.
I don't usually add Flourish excel to this tank but did this time b/c of an algae problem.
So I added that.
Few hours later when I went to feed them, I noticed one of the clowns resting on one of the heaters. I thought it was odd, but didn't think much of it b/c it swam away when I got close.
Next morning, woke up to find one of the clowns dead. I'm assuming it was the same one I saw on the heater.
Nothing was physically wrong with it. No strange marks, no bloating, not skinny... looked like a completely healthy loach... and it died.

I did another water change and haven't used excel again since that one time.
Now though, I'm nt sure if it's just paranoia on my part, but to me, it appears as though another loach is acting strangly. Also, they're not coming out as often as they used to, specially during feeding time.

The one that I can actually see that's acting strangely, again, nothing is physically wrong with it. Colors look great, no bloating, not skinny, no signs of anything.

Any info would be great. I'm just so worried that I'll lose more of them before I can figure out what's going on.

 

[aaronnorth]

they are more senstive due to being scaleless, however, i have never known any fish be sensitive at the recomended level, when you OD is when you start to get problems.
it only lasts 24hrs in the water column anway, so you can be assured there isnt any remaining in the water column.