Okay, thanks. I'll move tommorow the guppies back to my other tank.Since your tap nitrate is 10-15ppm I think your tank is OK at 20-25ppm. I like to suggest 25% water changes weekly to keep nitrate low and remove contaminants that we can't test for. Fresh water is usually enjoyed by the fish anyway.
Your pic showed up and the temp appears to be around 82F. As long as you are in the green section you should be OK.