New tank

[Filippo]

I set up a 36 gallon tank a couple months ago. I waited a a couple weeks, added a few fish and lost them all. I waited a couple more weeks and added some guppies and mollies and they are THRIVING. Since then, I’ve tried adding more fish. Tetras, platies, angelfish and every time they die within a day or two. I’m dumbfounded as to why the guppies and mollies are perfectly fine but anything else I try adding dies. Am I picking the wrong fish? Should I just stay with guppies and mollies? Any help is appreciated.

 

[SaraB]

Did you do anything to actually cycle your tank? Or just leave it filled with water with the filter running?

 

[DanThaFishMan]

It would really help out to know your water parameters. Ammonia/nitrite & nitrate levels and pH level. Also when you started the tank did you properly cycle it, either fishless or with fish? As far as some fish doing fine and others dying it might have alot to do with they type of fish. Some species are great for new aquariums because they are hardy and able to deal with the stresses of ammonia spikes and higher nitrate levels during the cycling process while others just can't hang in there. There are quite a few videos on YouTube about this. I just finished setting up a 72 gallon tank a few weeks ago and it's just about ready for fish. I used some old dirty filter floss and bio balls from my 55 along with API quick start to speed up the fishless cycling process. I did not dose the tank with ammonia at all. I only used one teaspoon of fish food in the begining and no water changes until my levels zeroed out with just a little bit high nitrate level reading then I did a 60% water change and waited a few days. All my levels are now at an acceptable reading and I will be adding fish next weekend. I can't stress enough that this process is crucial to the survival of most fish and you must have some patience. If you didn't "seed" your new tank the cycling process can take quite a bit longer. My first tank took about 8 weeks to fully cycle and I lost quite a few fish by not being patient. Also in the very beginning I found that you don't need to test the water every day. I tested mine about every 3 days.