I have a180 ltr tank which I have had for 4 months. For some reason there is an ammonia spike which I cannot get rid of. I tried doing water changes but although the ammonia dropped to .25, it has crept up again and is holding at .50.
This is what I may have done to cause it, but I don't know if this is right or not.
I cleaned out the filter after 3 months for the first time on advice of LFS. Put new white wool in top, new charcoal filter, squeezed out blue sponge under it in tank water, did npot touch the bio nood at the bottom and emptied out the dirty water in the filter unit which is a canister underneath the tank. Hoovered out the gravel and did a small water change of 10%. Might have been too clean and tidy do you think?? I don't know why the spike has arrived and is staying. I have one platy, 4 mollys, 4 guppies and 2 corys.
LFS told me not to do any water changes as this was removing the good bacteria required to neutralise the ammonia, and not to feed the fish for 3 days,, also to use Cycle for 3 days to build up the good bacteria.. Done this and the ammonia is still the same.
What can I do? LFS has told me to go through the same procedure again. 3 days of Cycle and no food for the fish for those 3 days.
I can see what he is saying by not doing water changes as it is weakening the good bacteria, but I feel the fish must be not happy in this water, although they look fine. If I start water changes it will just be an ongoing thing which will need to be done every day to weaken the ammonia. Why should it not be reducing, when I am withholding food and using Cycle?

I clean filter sponges and ceramic media every three weeks in old aquarium water, it doesn't matter when you first do it as long as the tank has established itself properly.

I am skeptical of the advice dished out by the aquatic store, and with all seriousness, I'd steer clear of them. Nitryfying bacteria can't colonize the water column, you'd find very few (if any) if you were to put a water sample under an electron microscope. They can only colonize hard surfaces to work efficiently, and they work more efficiently in dark conditions, such as inside the filter.

Water changes are the best thing to do when you have an ammonia spike, to immediately bring down the ammonia to safe levels. I'd send the cycle to the trash. In nine cases out of ten, cycling products either contain dead bacteria or the wrong type of bacteria. How can bacteria survive for prolonged periods between the date of manufacture and reaching the customer whilst inside a plastic bottle?

It might take a few days for the ammonia to fall to safe levels. Step up the water changes (I'd suggest 40%) and cut out the feeding until the filter can catch up.

Havent got a tank but had major amonia problem in my koi pond. Zeolite absorbs amonia. It comes in inch or so sized chunks. I put some in a net bag in the filter. You have to leave in for about 3 weeks. Then take out and soak in water probably overnight then rinse it and once its recharged you can re use it. Might be worth asking a tank specialist if they have used it in tanks. Other than using the zeolite all we did was water changes and cleaned the filter. Dont know if this will help but zeolite deffinately absorbs ammonia. Worked in the pond.

Every 3 weeks is way too much.

Ammonia levels may be caused by a mini cycle,as you are washing away good bacteria.
But,you could also have a dead fish,leaking ammonia into the water.Do a head count,see if all your fish are there.
Ive had my filter for 4 months,and only cleaned it the other day.I could have left it longer! I had a reading of 0.5 ammonia after that too.
What I did,was add a bottle of tetra safe start.Its wonderful stuff,its settled the next day

By the way,take your carbon out,and replace it with a normal sponge.Carbon is used to remove medication from the water,and could stop the cycle you are using from working.
But Tetra safe start is better than cycle.Cycle has little effect.

A few weeks back I couldnt get my levels down despite doing several water changes. I ended up taking all the rocks out from the tank to clean them and found a rotten prawn which Eric had half burried in the sand, I removed it and did another change and levels have been fine since

Holly is right, there may be a dead fish in there somewhere, or some rotten food??

Au contraire, I've always washed out my biological media every three weeks, it certainly isn't excessive and it's carried out in this way by thousands of fishkeepers. A quick squeeze or a rinse in old aquarium water won't remove too many bacteria, and in either case, they'll soon replenish the numbers that have been lost.

Talk about making work for yourself.
All you need to do,for a general maintainence,is change 10% water every week,and replace with conditioned water.Doesnt even need to be warm water,unless your fish are mega fragile.
My fish are dirty,and malawi need to be over stocked.I have to change 30% weekly,but i am running a test,and test nitrates,and when they get to 40 I do a change.Ive got it to 2 weeks,without needing a change. I feed 5 days out of 7.

It's not 'making work for yourself', it's a simple job that should be carried out, it's all part of basic maintenance. Detritus that collects in the filter can reduce flow rates and therefore reduce the amount of oxygen that reaches nitrifying bacteria, reducing their efficiency. The main part of the filter (i.e pipework) should be cleaned at the same time.

It's quite simple!

It would depend on your filter.If you have a good filter,for the tank size,its just not needed.
If your filter isnt very powerful,then you will have to do more cleans.
Over filtering is always a good thing.
I think if you joined a fish forum,they would tell you the same.