I have a 55g tank with two juvenile Oscars (there moving to a bigger tank when there bigger) I'm currently using a cascade 700 canister filter. I have to do a 25% water change every other day to keep the ammonia down. Should i get a new filter and if yes what type? I am think about getting the cascade 1200 or the cascade 1500

thanks for the replies

Okay, a few questions first. How long have the fish been in the tank, and did you cycle it first? You should not have ammonia present in a cycled tank. What are the ammonia readings, I assume you have been testing the water? I would strongly advise you to feed sparingly at this time, it will reduce the amount of waste going into the water. Anyway, if you could tell us your situation, we may be able to help you. Keep up with the water changes while the ammonia is still present.

Ammonia is very bad for oscars

I would up your water changes to everyday. As OFL says feed less. How long has the tank been set up for. If you had other fish in it before the oscars was the tank running without any fish for any period of time(and if so how long)

If your oscars are about 4 inches or above you should be feeding once a day what they will eat in 2 mins, less than 4 inches twice a day for 2 mins. I would half this until you get the ammonia to zero.

On the subject of filters you cant over filter so the bigger the better

the fish have been in the tank for months.
About a month ago the filter i had broke so i got a new one the cascade 700. to compensate with the ammonia i started using AmQuel Plus. I later found out after using it that any ammonia test kit using a Nessler reagent won't work with it. I only found 2 companies that made the other type of test kit. Aquarium Pharmaceutical and Kordon. Kordon is the company that makes AmQuel Plus and on there site it says that for unknown reasons Aquarium Pharmaceutical test kits will not work with AmQuel Plus. The only option i had was to get the Kordon test kit but it's 20 dollars for 10 tests. I haven't ordered it yet because i don't have the money.

I talked to a customer service person at Kordon and they told me that there product is so great that you don't need to use a test kit with it because it's perfect. I think that this customer service person doesn't know what there talking about so i stopped using AmQuel Plus and my test kit should start to work fine again within a week.

ok so i am guessing that by the time you added the new filter all the good bacteria in your old filter died or you didnt put the media from the old filter into the new one. If that is the case you are starting again with your filtration and are cycling your tank.

I have not heard of AmQuel Plus but i am guessing it is one of those products that 'get rid of ammonia'. What they actually do is change ammonia into a non-toxic form. The problem is that when you test for ammonia it still shows up on a test for ammonia. This will be why you are still showing a result for ammonia. If AmQuel Plus is a product for 'removing ammonia' i would follow the instructions and not worry that your test shows ammonia. Do water changes as per the instructions and you will soon find the ammonia goes down and nitrites start to rise

I suppose we have got to put our faith in these companies that manufacture of these products that claim to remove toxins. I've used them myself in the past, they are very handy when things go wrong. However, telling you that you don't need a casket because the product is a good is both irresponsible, and extremely arrogant. It is vitally important that any body keeping aquatic creatures always has a test kit. Okay, at least you've got a product that will reduce the risk of your fish being poisoned.

We need to address why you have got ammonia present. When you change the water, do you use water conditioner to remove the chlorine? Do you turn the filters off when you are put in the water back in? Have you been cleaning the filters at all? How much food have you been feeding, and had you been removing any uneaten food? And lastly, apart from the Oscars, how many other fish have you got?