Under Gravel External Filter

Hi,
I have a 350 Gallon fresh Water Aquarium.

Currently I have two pipe, one in the bottom of the aquarium linked to the in port of my external filter, and another pipe at the top of my aquarium linked to the out port of my external filter.

So the dirty water came from the bottom of my aquarium to the filter and then out of the filter to the top my aquarium..

The problem is that the quality of the water is very bad, and not clean at all.

So I am thinking to do the following:
- install undergravel filter and link it to the input port of my filter, in this way the dirty water is collected from all the aquarium and not from one point only..

Is there any negative sides for this filter, since it not a purely undergravel filter but a mixing between undergravel filter and external filter..

Also can I use sands with this type of filters or only gravels?

Thank you for help,

 

Welcome! Try to,stay away from the under gravel filters for a variety of reasons. What do you use as the cleaning element in the external filter - floss, cartridges or what?

 

I am just using carbon layer, and cartridge layer and a thin cotton layer..

How can I ensure that the dirty water is collected from all the bottom and not only once place?

 

I was checking online about the disadavantages of UGF, and I know verywell that they are not the best option for filtering.
but in my case I am not planning to use only UGF, but linking the UGF to an external filter.

So at the bottom of the aquarium I will have PVC pipes with holes just to collect the dirty water.. and the pipe is linked to a water pump (the in port) and the out port of the water pump will be linked to the input port of my external filter.

 

If your water quality is bad now, it's probably a problem with the filtration. Most gunk in the substrate doesn't rise up again, so it sounds like stuff is just passing through the filter.

What filter are you using on this tank? Can you post a few pictures of the setup?

 

350 gal is a hugh tank. Is the filter you have big enough to handle that big a tank. Your idea would make the ug act as a pre filter for the external which would become more of a biological filter. The gravel would also host bacteria. I like the idea but you would have to vacuum the gravel bed a lot so it wouldn't get clogged. If your water quality is bad you will have to do massive water changes to get it back. Are you testing the water? How big is your fish load?