Another reason for the high nitrates is that the tank is overstocked. I wouldn't even keep one Goldfish in a 10g. They are messy fish who produce alot of waste. They will also eventually outgrow a 10g. For all 4 of those, you should have around a 50 gallon tank with atleast twice the filtration.
Doing the daily water changes will take care of the problem now, but will not solve it IMO. I'd definitely start them to lower the nitrItes. Doing 50% water changes weekly after that and feeding once a day or once every other day will help.
You should really consider upgrading the setup though.
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*Kristin*
5 Planted tanks:
55g, 40g, 29g, 20g, 5.5g
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