I have a one year old betta in a 2.5 gallon aquarium with an in-tank filter. He started not eating about a month ago and I tried a round of tetracycline (removing the charcoal first). No effect. Tried penicillin and he perked up a little, so I kept it up for 10 days, as directed. He had started to eat a little and then someone suggested there might be an ammonia problem and sold me some Ammo-lock. I added just a little, but then decided I needed a kit to check. The kit showed a test of almost 3 TAN, but since the pH is 7 and the temp is about 78 degrees F, that is apparently an ok level. Just the same, I did a 75% water change, rinsing the gravel and putting the charcoal and a "bio-sponge", which is supposed to take care of ammonia (eventually), back in the filter. The fish is back to laying in the bottom of the tank, not eating. I'm tempted to completely change the water, but I'm afraid that will shock him too much. This little guy is trying to survive. Can you help me save him? I'm using bottled spring water, which I've tested and it's clear for ammonia, along with Stress-coat and I've added a small amount of aquarium salt whenever I've done a water change (as in throwing out much of the old water and salt). Help!