High Ammonia Levels In My 75l Tank

[menickb]

I have a 75 litre tank with 1 plec 1 humbug catfish 3 black widows and 3 mollies the problem is that i have high ammonia nitate nitrite levels the tank with fish belonged to a friend who just used to feed them an thats it i had the tank and fish off him and i bought a test kit and water treatment and everything else i needed i used the test kit and found high levels in everything and i cant get them down i have a under gravel filter a 12'' airstone and a fluval 3+ internal filter i cleaned the filter in tank water witch i took out of the tank to keep the bactiria in the membrane i have done two 50% water changes in the past 3 days and hovered the gravel i have no live plants or rocks i cant get the levels down p.h is 7 and the temp is 25 degres and i havent fed them for the past 2 days its not a new tank its well established never been completely emptyd the fish are quit happy and active but i worry about the levels as they can be toxic hany help would be appreciated

 

[rdd1952]

Hello menickb and welcome to the forum.

The tank isn't overstocked so that shouldn't be an issue but if the tank hasn't been maintained, there could be a huge amount of waste in the substrate that is causing problems. What exactly are the levels on ammonia, nitrite and nitrate? Are the tests liquid or strips?

I would suggest doing water changes as needed to get the levels down to .25 ppm of ammonia and nitrite. The nitrate isnt' harmful as long as it's below 100. You may also need to clean the undergravel filter as it may be so clogged that it isn't doing anything. After a while, "tunneling" starts to take over on the UGFs so the filtration is reduced. A good gravel clean should help with that.