I set up my 55 gallon cichllid tank about three weeks ago, and I think it cycled remarkably fast. The LFS owner lent me a bag of his cycled substrate, and 10 days after starting the cycle, I had already seen my spike in ammonia rise and fall to zero, my nitrites rise and fall to zero... but my nitrates have stayed fairly low through out this whole process. I haven't test my water for a couple of weeks, because all my testing tubes broke and I had to order another API test kit from Amazon. Got it today, and here are my reading...

Ammonia 0
Nitrites 0
Nitrates 5ppm

I had fish in there throughout the process for the original source of ammonia to start the cycle, thus I don't think there was too little start up ammonia.

Is my tank properly cycled? And, what is an ideal reading for Nitrates?

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55 Gallon Marine FOWLR Tank ( Yellow Tang, Flame Back Angel, Tomatoe Clown, Diamond Goby, 6 Line Wrasse, 4 Stripe Damsel, Blue Damsel, Kupang Damsel, Yellow Damsel and 3 Blue/Green Chromis)

you're good up to about 40. once you get to 40 is when you need to do a water change to bring the levels back down. but if you've been doing regular water changes (which by all means is good), then the level would never have risen so a lower number is to be expected

it sounds like it cycled. pre-cycled media can surprise you just how fast it can make a new tank cycle

I'd say keep testing weekly for a while just to make sure every thing has leveled off


my 30 gallon stays at 0 ALL THE TIME, but that's because the live plants in it eat up all the nitrates

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My 30 gallon planted freshwater - CONSTANTLY CHANGING

There is no proper value for Nitrates. As your tank ages they will slowly accumulate. They are removed by water changes, plants or denitrification (biowheel, UG filter). When you start a tank they should be near zero (as yours are). Your tank did cycle very fast so I would be careful, some of your readings may not be right. Add new fish very slowly.

In the beginning they are always low when you're tank is finishing up its cycle. If I had to guess I would say that eventually you'll see higher readings as you get closer to your water changes. Especially with the fish you have in there. Some seem like they would be big waste producers.

For nitrates, the lower the better. When you initially cycle your tank, there will just be none, unless you have some coming through your tap water. Regardless, in a fish only system you wont ever find yourself crying over not having any nitrates, nor will you find your fish upset about it either.

As your nitrogen cycle gets into full effect, your nitrates will climb, as noted 40 is when you really need to do a water change, I dont even let mine get that far, but its preference what will work best for you: Time available, Size required for a decent change etc.

In planted systems, the plants will consume the nitrate to a certain extent, this will reduce your nitrates in your water, but unless you have loads and loads and loads of plants, your nitrate will still climb up gradually. Some people claim that with enough plants, you dont need to change over water, I do and don't agree with that statement, but for what your question is, it should suffice to show that the plants simply do consume the compound as foodstuffs.

Low Nitrates = happy livestock (so long as your nitrogen cycle is in full effect! which yours is.: NH3/NH4+ > NO3- > NO2-)

EDIT: It is still important to add livestock slowly as noted, the bacteria responsible for converting these compounds have established in numbers appropriate to what you have now, when you add a fish, they will have to increase their numbers to compensate for waste. This is why mutliple fish added at once is frowned upon as it adds unnecessary stresses to the fish already in the system, and the new ones also.