So I cycled my tank for 7 weeks. Added some stability for the first week. I was just busy moving into my house so I didn’t get around to adding fish sooner. Well I added 2 clownfish thinking that it was fine because I checked the water 2 weeks prior. I ran a water test and I had very little ammonia which it was between 0-.25, well my fish didn’t make it. And I still can’t get the ammonia out. I’ve done 3 water changes and it’s still there. Any ideas on what I can do? I’ve only added a heater. The rest of the tank is stock.