What am I doing wrong?

[sschro13]

We have a five gallon tank with 1 beta, 1 corydora catfish, and 4 platies. In the 3.5 weeks we’ve had the tank, I have had to clean it thoroughly and change the filter four weeks already. I feel it gets murky very quickly.

The lady at the pet store assured me it was a good number of fish for the tank but I’m wondering if it’s just too many fish? The last couple days the beta stays low to the bottom of the tank and isn’t super active but I just cleaned the tank again today so we will see if that makes a difference.

Fish are fed once daily- flakes and pellets. Plenty of places for fish to hide within the tank. Conditioning drops are used with cleaning.

 

[Andy Sager]

For starters, your hunch was correct, you have too many fish in the tank. A 5 gallon tank is not really large enough for platies as they mature and if you have males and females, that tank will easily get very over populated with babies. I would suggest finding a different fish store as this one apparently is more interested in sales than the fish's health.
As for the filter getting so dirty so fast, that is usually a sign of overfeeding. How much food are you feeding? Your fish will be better off if you were to feed them more than once a day. A " standard" amount of food is whatever amount they can eat in 2-3 minutes and fed 2-3 times per day. This way, you are feeding less food per feeding and since the fish should be eating it all, there is little to none of it going into the filter.
At only 3 1/2 weeks old, the tank should be starting to go through the nitrogen cycle. Are you testing the water for ammonia and nitrite? What kind of water change schedule are you doing?

Let's start there.

 

[Andy Sager]

I'm not sure if this is allowed so if it isn't, please remove it BUT
Here are some common lies told to beginners as told by Dr Tim himself: 55K views · 773 reactions | What Stores Won’t Tell Beginners Some fish stores make things sound too easy. They say you can set up a tank fast, feed one food, and mix any fish. But a good tank takes time, different foods, and careful planning. Learning more can help you avoid costly mistakes. Comment below if you want to avoid common beginner mistakes and set up your fish tank successfully. #FishTankSetup #AquariumDietVariety #SaltwaterVsFreshwater | DrTims Aquatics