Filter for 37g goldfish tank

+1 on shaking the nitrate bottles. For the life of me I couldn't figure out why I was getting a zero reading on nitrates that I knew should be much higher. Took some asking around and finally a suggestion from someone here to bang the bottles on the floor or the table for 30 seconds before trying to test. Worked like a charm. All the sudden nitrates were reading as I had expected them to.

Plants will help (check out the threads for nitrate removing plants in the filter itself - I'll think of the name of the plant later... golden something or other...) :)

Good luck!
 
You haven't said what kits you are using yet. My guess is either not shaking API kit, kit is expired, or you are using strips. In any case it is almost impossible to have a tank with goldfish in it with 0 nitrate.

Plants can do it and with the right food for the goldfish you have tons of options for plants in the tank. I have had swords, vals, onions, cabomba, anacharis, lotus, and many many others with no problems. If the fish are getting the right foo to begin with they won't need to go after the plants for nutrition.
 
SUNSUN HW-302 should do the trick. It has a really good media capacity (which i believe is more important than turn-over rates) and is easy on the wallet.
 
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