Okay to get shrimp?

[Smalltank3]

I bought 6 ghost shrimp about 3 weeks ago and all of them died that night. I later found out that they died because of the ph chemical I was adding( I know, I never should of added it, big mistake!) So far from then, I did a 30% water change, then a 50% a week later, Then I switch my gravel to schultz aquatic soil and with that a 40% all without adding the ph chemical. With that totaled up, I changed 120% of the water that had the chemical in it. I've been testing my water to make sure of not having a mini cycle and my ammonia and nitrite are at 0. As of right now I don't have any algae, but I was thinking about getting shrimp in 2 weeks right after doing a weekly 30% water change. Would it be fine getting shrimp without the fear of losing them to the stupid ph chemical? Would getting an oto be best for cleaning walls and the shrimp being a scavenger and algae cleaner for my plants or just getting shrimp and not the oto?

The shrimp I plan on getting are cherries

 

[Seiryoku]

Percentages >.<

You didn't change 120% of the original water, I don't think.

100%-30%=70% (70% being how much of the original water is left)

Then you did 50%, but you only changed 50% of the 70% that was left.
70%-50%(35%)=35% of the original water left.

Then a 40% change.
35%-40%(14%)=21% of the original water left.

That is how I think it comes out. If I'm way off I blame my math teachers in school.

You changed most of it though. I'm not sure how fast the chemicals disipate on their own, so I can't say if its safe yet. I typed up a bunch of crazy math though!

 

[PsiPro]

If you use carbon in your filter, change it then let the water run for another week, i will work itself out as the carbon removes the copper (what is a common killer of shrimp).

I breed and sell cherries on ebay, so I can help ya if you need some. Also check the lounge, i'm going to be posting an ad for free shrimp in a min.