Nitrates, I am confused

[muskieswen]

My tap water is around 0 ppm nitrates, but when I measure the nitrates in my planted tank they are around 5 - 10 ppm. This is measured about 3 days after the water change. I do water changes weekly. Can I safely assume that my plants are not using the nitates (hence the algae problems and the slow growth) and that the nitrates that are there are from my fish poo? I have also 4 - 32 watt lamps and I inject c02 from a compressed bottle. Thanks for any info you can give me.

[carpguy]

How big is the tank? What sorts of how many fish? What sorts of how many plants? Ferts? Water changes?

The fish are at one end of the nitrogen cycle. A couple of bacteria later there's nitrates. If your tap is 0 and your tank water isn't, its the fish (and the bacteria). Without the plants your nitrates might be higher, a little higher, a lot higher.

Hard to say.

[Captain Hook]

Do you have a low amount of plants? Are you seeing alot of growth?

[muskieswen]

55 gallon tank, not many plants, I think more would me better. Fish are as follows:
4 cory
4 rummy nose tetraes
3 cardial tetras
2 harliqin rasboras
7 guppies
4 baby guppies
2 yo yo loaches
4 sae
4 ottos