Tank Cycled But High Ammonia Returning

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Puddles92

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I have a 25l tank with 4 guppies which has been set up for about 6 months now.
It had fully cycled within the first 2-3 months of us having it but now the ammonia levels seem to be creeping up again. Today we had readings of 1ppm ammonia, 0 nitrites and 1ppm nitrate so the cycle is happening.

We recently changed a filter pad as we thought this might have been the problem as it says to change it every 4 weeks but we have not seen any improvement.

We are currently doing 40%. Water changes every second day to try and keep it down.

I can see a layer of gunk beginning to build up under the gravel. Should we completely empty the tank to sort this or just try and get in with the syphon.
 
40% water change with a reading of 1ppm ammonia will lead to 0.6ppm ammonia still in the water, therefore unless you do a couple of 50% water changes in a row to reduce the level to 0.25ppm or even larger to reduce to 0, then you are wasting time as that 0.6ppm is still lethal to the fish.
Changing the pad with a new one made it even worse. These need no changing unless they are falling apart or you have other reasons to change them, such as with improved media, and even then you can't change more than a quarter in order not to cause a recycle.
Have you tested the Ph? Is there a change to what it used to be? A Ph crash can cause the bacteria to malfunction, leading to spikes.
Other reasons could be if you washed the filter pads in non-dechlorinated water, dead fish somewhere, something rotting like food left overs, too deep and dirty substrate, etc...
 
The thing that jumps out at me is that you changed the filter pads. This is where the good ammonia resides and the reason for cycling the tank. If by some chance you still have the old ones, put them back in the filter.
 
Yeah I don't understand why idiot companies advise changing filter media when they hold all the necessary beneficial bacteria. Wheeze them out every now and then in old tank water on a water change by all means but don't put in new media!
 
Puddles92 said:
I can see a layer of gunk beginning to build up under the gravel.
The replacement of the filter pad has been mentioned, so you are likely back in a fish-in cycle again. But the part quoted doesn't appear to have been addressed... What sort of gunk is this? More than likely it the result of excess waste, old food, detritus, etc. this needs to be siphoned out. You don't need nor want to remove all the gravel, because this could release excessive amounts of ammonia into the water, but it does need to be vacuumed out. With each water change you need to siphon as much of this as possible, without disturbing it where it's not going up the tube. Do this with each water change and increase the size of your water change, and the ammonia levels should creep up less quickly and be safer for the fish. Also using a dechlorinator like "Prime" that detoxifies ammonia will help also.
 
Thanks. I shall do some larger water changes today and see if I can siphon out some of the rubbish. I have been siphoning the gravel but only the top layer so I guess I need to get right down to the bottom.
 
I've also hear you shouldn't do more than 25% gravel clean in one go, as this is where bacteria grows also.
 
Arcticfox1977 said:
I've also hear you shouldn't do more than 25% gravel clean in one go, as this is where bacteria grows also.
 
 
Some of the bacteria do live there (as they can on any surface) but these bacteria "cling" to surfaces.  Just doing a simple gravel vac will not dislodge them significantly.  Its not much different than giving the filter media a quick "swish" or "rinse" in a bucket of old tank water. 
 
As you pull the "muck" up from the gravel, you are just increasing the water flow over the rocks (and by extension the bacteria).  The water in your filter moves faster than that and the bacteria can cling to that media just fine.  So, it isn't really an overly big concern that gravel vaccing will cause a mini-cycle. 
 
The danger (and what gets some folks in trouble) is kicking up too much muck in the process, especially if its been too long since you've done it, and it starts to break down faster, releasing more ammonia into the water column.  The key is to do it carefully once its started to visibly build up.  Try to not let little bits loose that aren't immediately sucked up and out.
 
As Eagles said, kicking up gunk into the water column will cause more ammonia, so try to suck it up without and the best option is large water change after each thorough vacuuming.
 
There is more nitrifying bacteria in one's substrate than most realize.
 
As for swapping out media, pads intended to remove mech waste should be well rinsed or replaced. Filter floss is a prime example. Media that clogs easily is not where the bacteria colonize. On the other hand, one should swap out bio media as infrequently as possible. Just rinse to keep it as unclogged as possible.
 
Deep vacuuming can have negative consequences in two ways. As noted it can stir a lot of stuff into the water column that isn't wanted. But the second component has to do with the nitrifyers living in the top portion of ones substrate. They are near the surface because they get lots of ammonia/nitrite, oxygen and carbon flowing over the surface. When we deep vac we tend to turn over the gravel some. We pull gravel with no bacteria up from deeper and some of the surface gravel ends up deeper where it cant really survive. So it can be a double edged sword.
 
However, the amount of information on the tank is way too scant to be able to determine exactly what is going on. What I do know is if you have had ammonia showing up for a number of days, you should be seeing some nitrite. So far you say its 0. This always makes me suspicious of unexplained ammonia readings.
 
Without knowing your pH and water temp. it is not possible to determine if your ammonia levels are a real threat to the fish. Even at 1 ppm. It could be safe for the short term if your tank is at a pH of 7.5 or less.
 
One good clue as to what may be going on is how your fish are behaving. If they are not acting as they normally do, if they are at the surface a lot, if they seem to be less active or swimming differently, if they are not eating or hiding a lot, these are all things that would indicate they are in distress. On the other hand if they seem to be acting and eating normally, there is a possibility that some form of testing error is at work regarding the ammonia kit.
 

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