Water Change Gone Wrong?

Question
QUESTION: I have a 33 gallon fish tank with the following:
4 Zebra Danios
2 Glo Fish Danios
1 Angel Fish
1 Gold Gourami
1 Black Ghost Knife Fish (Being moved into a bigger tank when he gets bigger)
4 Neon Tetras
1 Golden Wonder Killefish
1 Emerald Green Corey
and
4 Serpae Tetra

I did a water change tonight because I've been dealing with a brown algae treatment...(White Gravel...never again)

I used a bucket that used to have cat litter in it...but I didn't realise there was still a little bit of dust from the litter in the bucket until after I poured the water into the tank...will this harm the fish? I put the water conditioner and stress coat in the water before I poured it in...I'm worried 2 of my danios seem to be very lethargic. It's only been 10 minutes since this happened. It's taken forever to get my angel fish to the size he is and I don't want to lose him!

ANSWER: Christa,
the cat litter won't hurt anything.
I would be more concerned with what you used to kill off the algae and how big of a water change that you did.
If the algae treatment was copper based that can be a problem.
If you changed over 30% of the water volume you can change the chemical balance of your aquarium.
A few more details please and we will go from there.


---------- FOLLOW-UP ----------

QUESTION: I used a product called Algae Control by Tetra. I have used it in the past with no problem I put the proper dosage in and removed the filter bag...that will be put back in, in the morning as it says to wait 6-8 hours to replace the carbon filter bag.  I did a 10% about a 10% water change to get rid of dead algae that was settling down into the gravel.  I put enough to treat 24 gallons in because the directions go by 1 ml per 12 gallons for some reason.

Answer
Christa,
Well looks like there are no issues there.
I would take a quick check of the PH and make sure the temp is correct.
Also if you have a test kit, check for ammonia, nitrite and nitrate...
I have a sneaky feeling the PH could have been erratic as that can cause this type of behaviour.
Let me know.