No filters in your water filters?
BigJim is giving you good advice. Water changes are not going to shock your fish if you do it correctly (match water temps and use a water conditioner) however if you leave the nitrites that high, it could (will) kill them. I wouldn't be doing anything less then 50% PWCs as previously recommended...and Yes, it's going to take multiple water changes (not just 1x per day) to get that level down to a more acceptable point. Remember, anything over .25ppm ammonia or Nitrites can harm your fish.