need help here

[cougargirl50]

Ok I got a 20 gallon tank. I have 6 zebra danios and 5 platys in it right now. A friend of mine was getting ready to get rid of his tank and needed someone to take his fish or he was going to flush them. So me getting really into the fish thing, told him that I would take them.
I knew I would probably be overstocked but didnt want to see the fishy's die. So I took them, and put a algea eater (i dont even know what kind it was) 2 tetras and a platy. I was going to do that till I got my other tank up and running.
Well I decided that I didn't want the algea eater, and the 2 tetras so I took them back out today. I only put them in last night, and took them out this morning. I always do a water change on sundays, so I did my normal water change tonight and I found that my levels have gone up a little.
My
PH 7.2
Ammonia .50
Nitrites 0
Nitrates 5.0

I have never had my nitrates to 0 yet since I had my tank and thats been over 2 months now almost going on 3. But I did have my ammonia at 0. Did my ammonia levels go up because I added the other fish? Oh yeah and I took notice that when I took the fish my friends water had a green tint to it because he didn't have the filter running, or the heater. I know that isn't a good sign.

Can someone help me??

[Betta-Gurl]

Did you add your friends water to your tank? if so it might have affected your levels.

[anonapersona]

Yes, by adding more fish to the tank you have increased the load on your filtration system. The system will catch up, but it takes time. For now the best thing to do is to feed a lot less and change more water, maybe twice a week, or as needed to keep ammonia low. Since you removed the added fish, it all may settle out quickly. Keep testing the ammonia and change water to keep it as close to zero as possible.

[scottracy]

anonapersona is correct, an increase to the bio-load means the current bacteria colonies will no longer be able to process all the waste produced. I had to house 9 small platy in one of my 55g for a few days. I did a few extra water changes and cut back on the feeding. My water parameters did not change and the fish did well! How long have you had your tank running?

Scott