Help Please

[ArthurSmith]

Please help, I am fairly new to tropical fish keeping, maybe 18 months. Recently all my fish died so I basically started afresh, new filters, carbons and removed 50%water then cycled we no fish for 3 months. Added 8 small fish, 6 died within 3 days but 2 zebras survived for a few weeks then died in last few days, not sure of symptons but some are getting stuck in the filter or behind it/on top. (Stingray 10).
Anyway I bought a master test kit and have just tested everything to sort the water before starting again. I removed maybe 20% last night and rinsed the large sponge as rinsed the small one a week ago (in its own water before dumping). My NITRATE is obviously really high as is my PH but I am not sure how to fix the problems?
Water is normally changed every fortnight or when the tank starts to look dirty. It is all decorations in the tank, no live plants. Only thing ever added to the water is tap safe at water changes. I have no scents etc in the room.
 
Tank size: 42 litres
pH: 7.6   High PH 7.8
ammonia:0.25
nitrite:0
nitrate:160
kH:
gH:
tank temp:28
 
 

 

[Asteria]

With nitrates that high it would be the cause of your problem. By the looks of it.
Test your tap water for nitrates to see what it's coming out the tap at.
Just doing water changes can sort this as long as the tap water does not have high nitrates itself.

Ammonia should also be at 0.

 

[Akasha72]

Hello and welcome to the forum.
 
Adding some live plants would help you massively. Live plants take up Nitrate as food and they can also help with Ammonia too - although I don't rely on plants for that. Ammonia should always be zero and if it's not you either have something rotting in the tank that needs removing or you are over cleaning the filter. 
 
You mention a new filter ... have you moved the old media into the new filter? If the filter has brand new media too then you are beginning cycling this tank from scratch. If you are unfamiliar with fishless cycling (which we will always recommend here) then pop over to the beginners section and have a read there at the wonderful advice on cycling your tank before you add fish.

 

[jag51186]

Also, to add to what everyone else said, when you are rinsing the sponges...are you rinsing them in tank water or water from the tap?? If you are rinsing with tap water, you are probably killing your good bacteria and going through mini cycles every time, which probably is spiking your levels.