Fast droping Nitrate levels killing fish?

in the tank i have a fake plant and on the branches of it there are like strings (kind of like spider webs but thicker) with what looks to be dirt attached to it .Im guessing thats not good and i should clean it right?

 

Im no expert but i can tell you this. You will have a heck of a time with a 5 gallon tank.

When something goes wrong, there is hardly any time to notice it.

I would make sure you keep up with the water changes. Also get a detoxifier like Prime , to instanly detoxify the water when you have high readings.

I would also recommend a product called Cycle .
But don't rely on the chemicals alone keep doing your water changes.
And if you havent got one already I recommend a Master water testing kit.
I would also consider getting a bigger tank.

As mentioned in the beginning Im no expert, but ive had sucess with the items mentioned

 

ER may be more going on

HI,
Many times in freshwater we only worry about NH3 and nitrates, but another common problem is PH shock from biological filters.
What works for me is to prevent the PH spike by adding a small amount of crushed coral to a media bag in the filter if the PH drops to 7 or lower a small amount of the buffer in the Calcium carboante will be dissolved this can occur in freshwater much easier than salt.
So maybe only 2 table spoons of that calcium carbonate (crushed coral).
I have used this for the past 20 years in all my fresh water tanks.
My africans of course but most liver bearing fish need stable PH and many of the freshwater cichlids can handle a higher pH if there's no PH crash.
so in closing most problems are really loss of carbonate in the water due to metabolic uses by bacteria this results in a PH crash this will kill more fish than NH3/.
Doug