About my tank (3 month old Planted Goldfish tank): Its a goldfish tank, 30G, 2 goldfish (total size around 16 inches) plants and moss with huge filter and extra filter. Water has been pristine clean for months. It only goes slightly brown when i gravel-vacuum during WC. I do 30% water change every 5-6 days regularly. and once in a month do 40% WC on 2 consecutive days. I clear the filter once a month in stale water taken from tank, I do not clean the filter thoroughly but I clean the sponge halfway through and clean the other half thoroughly during next WC . this sponge cleaning is done every 2 weeks or max in 3 weeks. I dose my plants with plant nutrients every 2 days. And Excel dosage every 2 days. I dont dose excel on the day I do WC. I feed my goldfish pellets, dried bloodworms, flakes and greens. I normally feed them pellets, DBW and flakes (v high nutrients) in mornings and in evening i give them greens (i.e blanched lettuce, cucumber, broccoli ,)every 2nd day. otherwise its the same pellets flakes etc. The goldfish are not tiny, they are huge and need LOTS of food otherwise they finish it fast and keep scooping the surface for more. I sometimes even feed them thrice on sundays. On saturday, I feed them only once in entire day with just greens. The Problem: So i always see very high Nitrates in my goldfish tank, its a planted tank . VIDEO :- YouTube - 30Gallon Goldfish and planted tank Update: Feb-06-10 last month, when the fish were acting weird (swimming slow and not really perky) and water was SLIGHTLY Cloudy (i didnt change water for almost 2 weeks), i quickly checked water and there indeed was huge spike in nitrate (above 80 ppm very very red solution in testtube) and even dangerous nitrite was near 0.25 ppm. zero ammonia though. I quickly did 40% water change and repeated same next day (water was treated with prime). fishies quickly responded by going alert and playing etc and there was zero nitrite and nitrate was around 30 ppm. water was back to crystal clear. Actually I was sick after New year holidays and wasnt able to change water for good 14-15 days. So this didnt surprise me. yesterday , before doing water change, I again tested for nitrate, this time too, the nitrate has climbed up above 60 ppm. After WC it was just below the color of 40 ppm (so i say 30). what is the safe margin? I have read its safe if its at 40 ppm but is it really safe? I dont like this huge readings of Nitrates. (Ammonia, Nitrite always zero), The thing is water during all this months has been pristine clear (apart from that 1 time i mentioned above), When i go sideways to this tank i can see all the way across the tank and see filters and plants at far end . So water is totally clear. but the nitrates are high it seems. I read plants/algae are the ones consumes this nitrates and wc is the only gaurenteed way to remove nitrates, Is there any other way i can remove nitrates? whats causing this? Is my filter medium small? or I dont have enough plants to consume this nitrate? Anyone has trick up their sleeves to keep nitrates low? and magic Anti-Nitrate cubes i can fill in the filter? I might be overthinking and getting overconsious about this Nitrate issue but i just want to clear my thoughts and see is there a way I can balance this tank out. Oh and BTW i am soon going to upgrade this 30G tank to 46G and not going to add any fish. just 2 goldies. but this will take around a month and i want to see this tank stays okay. Attached: 1 )Pic of the readings i took month ago during that huge spike 2) the nitrogen cycle pic i got from some site, its been on my desktop since i learned about cycling some months ago.