Messed up cycle. Can it be fixed?

I goofed. How do I fix this?

I have a 4 week old 10 gallon tank, filtered and heated. It’s inhabited by Silky, an awesome female CT. Living with her are 2 Koi Swordtails and 3 Corys.

The tank has never been properly cycled. Not knowing any better, I took the advice of the guy at a pretty reputable pet store and came home with tank, fish and “Bacteria in a bottle” that he assured me would save me the pesky and time consuming chore of cycling the tank the old fashioned way. Since I live in a small town 1.5 hours from the store, the temptation was too good to resist.

You all know what happens next. Of course the “Bacteria in a bottle” doesn’t seem to work and the ammonia levels start creeping up. I’ve been trying to keep them in check with frequent, usually daily, 50% water changes.

So far the fish all appear to be doing well. Growing, eating, active, etc.

My question is this...at this point is there any way to establish a cycled tank without destroying these poor fish? Should I try more “Bacteria in a bottle”? I know that the ideal levels of ammonia and nitrite is zero, but failing that how high is too high? Right now I’m trying to keep things below .25ppm but I fear that I will never get the tank to cycle with the levels that low, and I fear casualties if I let it get too high.

Please go easy on me. I’m a beginner trying really hard to do right by these fish and making a few mistakes along the way. Thanks for any help you can offer.