4 years ago #1

Can someone please explain whats happening with my tank? I have been running my 48ltr tank now for 5 wks, 4 wks with fish 2xmollies , they both seem fine and showing no signs of stress. The Ammonia started to rise (1-2) and then small traces of nitrites started showing but never rose above 0.25. Was testing the water the other day and thought i would just test for Nirtates but didnt expect to have any due to seeing no Nitrite spike. To my shock i had a reading of 10-20 (hard to tell), ammonia 2-3 and nitrites 0.0. Been using API liquid testing kit as i've heard these are the most accurate! Tested the tap water so i no that these are true readings. Is it possible to skip the nitrite spike as i have been using Filter Start? But then i would have thought that the ammonia would be showing 0.00 if the tank had cycled. Someone told me i could be over feeding and thats why i have nitrates and was advised to reduce feeding to once every other day and do a couple of PWC which i have done but not much change in the readings today other than the nitrites have now reappeared and are reading at 0.25 Can any one explain what might be happening and how i can get the tank back on track? Iv asked a friend if i can have some of there filter media and water to do an instant cycle

4 years ago #2
Silver Member
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The quick answer is nitrAtes under 40ppm is fine, if it gets above that number do a water change.

To fully cycle a tank you're looking for first an ammonia spike, then a nitrite spike and then they both drop to 0.

Did you do anything to the tank the other day for the cycle to take a bit of a hit?

Do a partial water change and leave it for 24 hours, test the water again and see what it comes up with.

4 years ago #3
Fresh Member
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No not done anything different, forgot to mention that 1 of the mollies gave birth to 15 babies 4 days ago and they are in a floating hatchery tank. The pet shop has alot to answer for considering i should have been sold 2x males, lol. I no i need a spike in both ammonia and nitrites before i get nitrates, but don;t understand why i had a small trace of nitrites at 0.25 and then at zero. I by chance checked the nitrates thinking that they would be zero because ive not seen any spike in the nitrites. Why have i got high reading of nitrates? I was told that it may be due to overfeeding, so for the last 4 days i have reduced the feeding I have done 2x PWC of 25% in last 48 hours and the nitrites are showing back at 0.25ppm. Im lost really and i didn't want to do too many water changes incase this gets rid of any bacteria that i need to complete the cycle.

4 years ago #4
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It seems like the aquarium established a nitrogen cycle, then something overwhelmed it or removed much of the beneficial bacteria. Over feeding could be a problem source; it's OK to feed the fish twice a day, but try to give them no more than they actually eat in a couple of minutes.

My guess is the nitrogen cycle was interrupted by too much cleaning. The beneficial bacteria that make up the nitrogen <email> mostly in the substrate and filter elements. Thus, replacing all of the filter elements at the same time will remove too much bacteria. So will deep cleaning all of the substrate at one time.

For the next couple of weeks, you may want to do a 25 percent water change every three days. Adjust replacement water temperature to roughly that of the aquarium, and treat it with a good tap water conditioner. Some of the reformulated conditioners will temporarily neutralise toxic nitrogen compounds and take care of all the usual stuff. Stress Coat Plus is one example.

While removing water, syphon any debris off the substrate surface, but deep clean only about 1/3 of it in any week. If the filter elements get dirty, clean them by gently swishing them in used aquarium water. Clean or replace only one filter element in any week, and skip substrate deep cleaning during that week.

After the first or second partial water change, check the toxic nitrogen compounds. When ammonia and nitrite stay at zero and nitrate is below 40 ppm, the cycle will be functional, and water change frequency can be reduced to once a week. Fast growing plants like hornwort will improve water quality by ingesting toxic nitrogen compounds.

Good luck, and please keep us posted.

4 years ago #5

Hi thanks for the advice both. Johnarthur i don;t think the tank has ever established a cycle. im pretty new to this and I think a combination of over cleaning and overfeeding is probably the cause. Im going to take the advice of 25%pwc and feed only once a day and see what happens. I just want to see a nitrite spike and then i think i will be back on track with the cycle. I have today done some tests and these are the readings: ammonia:1.0....Nitrite:0.25....Nitrates:2.0, so not much change really. water temp is 26c.

Can anyone tell me what is causing the presence of nitrates when i've not seen a nitrite spike? Ive been testing the water every other day if not every day so i don't think i would have missed it.....and will the nitrites ever spike while i have nitrates????

Your knowledge is greatly appreciated. I will not be defeated, lol

4 years ago #6
Blogs: 115
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The nitrogen cycle grows in sequential steps, and nitrate is usually the last nitrogen compound to increase. It's not as reactive as ammonia or nitrite, so a nitrate concentration below 40 ppm is acceptable. Lower is better, but it would be unusual if nitrate were to measure zero concentration.

You may want to click on this link for a little more on what to expect while the cycle is growing:

3 years ago #7

I also did a cycle for 10 weeks and something simular happened to me, I actually was testing the water every other day and had two fish to cycle my tank... on week 11 and 12 everything read zero and no spike was ever detected anywhere. Decided to add more fish to get a cycle...still nothing... but that was not possible. I did not do any water changes or filter cleanings, waiting for some sign of cycling. We discovered that at some point the tank had completed its cycle in a 48 hr period between testings and I never picked it up on a test.After 12 weeks we began regular maintenance and everything has been good. My point is maybe the Nitrites rose and fell so quickly, you did not catch.

3 years ago #8

This is great information. I have had an issue with a tank for 2 month - nitrate spikes, cloudy water, etc. After reading this I believe my issue is that I vacuum daily through all the gravel and change at least 50% of the water.

I always have 0 nitrites and low ammonia but crazy nitrates. I also have been changing the filter each week.

I guess I need to stop cleaning so much. I have 2 other tanks (set up after this one) and both are doing fine but also have 0 nitrites.

Any ideas on how to increase PH?

I test the water in the morning and evening on each tank while I never saw a nitrite spike it must have happened.

3 years ago #9
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Filters should not be changed unless they are falling apart. Much of your good bacteria lives in the filter ...the rest in your gravel and decorations. Your tank is not cycling because you are throwing away your good bacteria every time you change your filter media. It is supposed to look brown and yucky...that is the bacteria that makes it look like that!!!!

When you are forced to change filter media, you should keep the old owne in with the new for a few weeks to seed the new filter.

3 years ago #10
Gold Member
Blogs: 0
Forum: 309
Votes: 12

I have been cycling a tank for 3 weeks now and test the water every 2-3 days and have never come across a reading for nitrites. They are always 0 but I do have readings for both ammonia and nitrates. I have not cleaned this tank at all and have used seeded filter media and gravel and have a couple of plants in there. It's a 5g tank. I thought it may cycle quicker than a large tank but obviously I was wrong. My ph is also very low reading at 6 but all of my tanks seem to have a low ph.

1 year ago #11

My God I wish I did not throw away that filter pad It was getting brownish. Now after 2 months I am still at beginning :/

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