A 25L Fluvel Chi tank is not very large and has a small surface area so fish stocking levels need to be kept low. What did you do when you say you "cycled it for a week'? if you meant you filled the tank with water, added plants, turned the heater on, then left it for a week, that is not cycling. 2 fish of lampeye size would be fine if you then left them for a month. This would have given the filter time to start cycling. At the end of the month, assuming your ammonia levels were negligible, you could then add 3 guppies. To add them after only a week was too many fish in too little water too quickly, which is why you had the ammonia spike. I do not know anything about zeopads so just looked them up. It says they absorb ammonia. Personally, I would have just done daily water changes until levels dropped. It is good you returned the guppies. The tank should cycle nicely with the 2 lampeyes in it. A few snails help keep the tank clean. Too many though become a pest. If you do not want them, squish them against the side of the aquarium, the fish will eat the remains. Dwarf chain loaches are not suitable for a tank your size plus they need a mature aquarium. The ammonia levels will be fine if you do not let them get any higher than stated (if they start to rise further, do extra water changes). I know you are supposed to have 0 ammonia but I have never yet had a test result that showed 0, even on a tank just filled with water and nothing added. 0.25ppm is as low as I have managed but it could be my eyesight that is the problem. Google images for aquarium cycling and see what you should expect over the first few weeks.