Murky water in my tank Help please

[Zipzap]

Ok, so I'm not really too new to aquariums, but I have a few questions to ask.
My water in my 20 gal is murky. I have tried replacing the filter cartridge and I cleaned it yesterday, with no luck. Suggestions?
I also have a Betta tank. He is separate from the other fish because I have a Gourami with similar colors.
His tank water is all funky too. I am going to change it here very shortly. I got the Betta tank from a goodwill along with plants and gardening gravel, which I did not use.
Ever since I used the plants, both my tanks have gotten horribly yucky. Betta tank had three and larger tank had one.
I have since thrown the plants away, but big tank water is still bad. I need help. I had a fish meltdown once already, and it was horrible, and I REALLY don't want another.

Can you help???????

 

[Samzter]

Maybe consider investing in a steriliser? Hope I spelt that right! Or possibly, I'm not sure of the prices but if you look on amazon, eBay or craigslist the may have some cheaper ones

 

[Cloudhp8]

How long has these tanks been set up for?

do you know your parameters? ( Ammonia - Nitrites - Nitrates)

What are you using for dechlorinating?
Are you using any chemicals outside of a water conditioner?

 

[Rivercats]

Plants won't cause tanks to get yucky unless they are dying and fouling the water.

How often do you do WC's and how much do you change out? Also when you say murky how so? Cloudy, green water, a lot of small detris in the water column? Posting a picture would be very helpful. When you do a WC does the tank cloud right back up? A UV sterilizer is only good for extended bacterial blooms and green water algae blooms.

Also as already asked what is your nitrate level? You need to post a lot more information about the tank, set up, and maintenance along with a picture before any specific advice can be given.

 

[Zipzap]

The water is cloudly, with tiny debris. I cannot post pictures because it takes an hour with my slow internet.
I have a water plant that isn't doing too good. Should I remove it?
I tested the water yesterday and today, and nitrite and nitrate levels are good.

 

[Rivercats]

What exactly are your readings? Good doesn't tell us anything. Also what about your light, what kind and what bulbs are you using?

Detris in the water column means your either not doing weekly 50% WC's or your filter isn't catching it. Use 100% polyfill in your filter to help remove small free floating detris. Also you could be overfeeding which can cause a lot of floating detris.

What kind of plant is it and what is wrong with it? Without knowing your lights or any other important info I can't give you any decent advice.