Help! Tank Not Stabiliizing After 3 Months

[bgdeeps]

Hi All,
I m very frustrated to see my fish again swimming at the surface in the morning today, I have changed water 3 days ago. and Fish are getting worse, I have lost 3 fish.
 
I had a perfectly working tank for about an year. 30 Gallon, planted tank, with 3 platy and 5 guppies, that is very low load.  I cycled it fishless and it never missed the parameters ever. and then I moved my tank 3 months.
As it is a planed tank I have a layer of clay ( something similar to API First layer - but its a german company) I have a layer of clay and then a layer of gravel on top of it. I had never vaccumed the gravel until then. During the move the soil layer and the gunk in the gravel got badly disturbed. I changed 20% of water. It settled next day, the water was all clear, After water change the ammonica and nitrite levels were 0. I use  API liquid test kit of test the water.
However since then the Nitrite and Ammonia levels have been erratic. Both ammonia and nitrite levels reach 0.5 ppm or more with in days sometimes and sometimes it is just nitrites, I bought a gravel cleaner which I m using to clean the gravel. I have been changing 10-20% water once a week. but the tank doesnot stabilize, It has been 3 months. Shouldnt the water go bad slowly and not quickly like this?? Why is it getting bad so frequently with so few fish?
The plants are not doing great but not badly either.
I tested the tap water, it was 0 ppm of ammonia and nitrites.
Should I change the filer?
Should I replace my gravel?
Should I do a 100% water change? Someone suggested me to not do this as the water also has bacteria?
Please help? I cant continue to change water like this every 3 days and still see my fish getting sick an dieing
 
 
 

The fish swim near the surface and go back when I change water.
The 3 guppy fish that died I suspect died from fin rot. I used melafix for a week after that. only 2 of them had signs of fin rot, but water conditions being bad all the time must have killed them.
The other fish dont seem to have fin rot, they are swimming stabbly at the moment.

and most of the times its the nitrites that are high (0.25- 0.5), It looks like ammonia to nitrite conversion is happening but nitrite to nitrate conversion is not happening. Is something killing off that bacteria?

 

[Blondielovesfish]

It sounds like you may be going through a monocycle. Why it has lasted so long I'm not sure.

How do you clean the filter?
Have you changed any parts of the filter recently?

 

[Mamashack]

Sounds like you disturbed the waste that had settled in the gravel and this has been releasing toxins into the water causing erratic water parameters. Best to only clean 25% at a time but regularly like once every 2 weeks or a month and do a different 25% every time. You'll probably need to do a larger water change and keep a close eye on the water parameters as Blondie says it may be going thro a mini-cycle - maybe do your water tests twice a day until things settle down and change the water whenever ammonia or nitrItes are present in any amount even 0.25ppm.

 

[TwoTankAmin]

I suggest the following to let your tank re-establish. Do not add meds or anything else besides dechlor. Do not over dose it either.
 
Stop vacuuming, this is very important. Once the tank settles down you can think about resuming. With a planted tank, vacuuming should be done less often as a lot of what you are vacuuming out is food for the plants as it sinks into the substrate.
 
Make sure your filter media is clean. Do not change any bio-media, only floss or whatever traps solid wastes. If you have only sponges, gently rinse them in tank water in a bucket and reuse them.
 
Monitor your ammonia and nitrite- ammonia should drop to 0 before nitrite. You need to keep these levels down below .5 ppm for sure via water changes and with all the fish have been through so far, under .25 is better- for ammonia especially.
 
My bet is several things happened that caused the problems. Organics got into the water column from turning over the substrate, but more importantly, that also damaged the bacteria living on it. How much of the bacteria in a tank that is in the filter is not a constant. Many things can cause the numbers there to be below average which means they will be above average in other places- such as the substrate.
 
Next, change how you feed the tank for a while. Fed fish are more resistant to ammonia but this must be counterbalanced with not wanting uneaten food in the tank which adds ammonia. You also don't want to feed a lot since, even if the food is all eaten, more food means more poop. I suggest you feed very sparingly twice a day. The key word here is sparingly. As long as they are getting some food, its better to feed too little than too much here. If the fish are not eating, get the food out of the tank right away.
 
Also, check the tank for any dead fish or plant matter and remove them. Other than this, try to disturb things as little as possible.
 
Finally, change your maint. routine. Once things settle out, change at least 1/3 of your water weekly and as much as 1/2. If your plants are only doing OK or worse, consider adding at least a trace mix fertilizer or possibly an all in one fertilizer which also contains the macro nutrients. Normally, plants consume ammonia and nitrate which can help with cycling related things.