my suggestions is to keep experimenting with all sorts of fish when I first started looking after goldfish I had them dying on me within days untill I had to change the water and they still died I say do what I did increase your luck by constantly buying fish and eventually they wont die it takes years of practice and expereince to reach looking after these types of fish I would say go for goldfish and cold water fish and increase your experience where I started off I was crap at looking after goldfish then when I first turned 20 i bought myself a tropical tank and I am going to get a 200 gallon tropical tank!!! jeez I am going to be busy and I will start my own breeding shead but they will all die I tell you why because I need to increase my experience even the most experted aquariests have troubles with fish like that dying fish is normal and we just need to except it I say dont just experiment with fish do it with water also and build up to it and never jump into the deep side I dont know you and I dont know how much practice and expereince you have in fish keeping so correct me if I am wrong I may not know but yeah just try that suggestion.