Skim the top or draw from the bottom? Freshwater tank.

[Desdinova]

Generally speaking, sump systems seem to be saltwater systems. However, I need to make one. I want to get oscars again, but they're so messy...

So I'm planning on a 2-part filtration strategy.

First, I'll just mention the off-topic part: Undergravel plates with a lift tube that I will attach a 1320 GPH pump to and suck all the bad stuff out from under the tank, once per month.

Now, back to business. Should my overflow sip from the top or draw from the bottom? I was always taught that you wanted to get the water at the bottom of the tank, because that is where the majority of the toxins are at. That's why tests should be done with water from the bottom on the tank.

Does that sound right? I've designed a custom overflow system for doing just that, but I don't want to have to build it if I don't really need to.

 

[duanes]

Many of the invisible undesirable constituents of water are attracted to the air water interface (the surface) this is why you can sometimes see scum/slim/oil buildup on the surface of contaminated waters.
This is also why fractionation works well (in both salt and fresh water) at removing these pollutants, when the air/water interface is agitated those undesirable constituents foam up and can be removed.

 

[backpack]

Skim from the top

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[Jc1119]

I'd skim from the top in either salt or fresh. If you direct the flow correctly and get good circulation around the tank, top skim. Aside from the safety factor in having your drains up high. Lower mounted drains can empty a tank quickly if something goes wrong.

 

[Apexden]

top is where the nasties go to, you can use a power head and aim in twords the bottom of the tank at the oposite side of the skim box if you wanted to

 

[tomomothy]

pulling from the bottom can help with getting mechanical stuff off of the bottom of the tank, but for bio skimming from the top is the way to go. If you can do both that would be cool, but given a choice pull from the top.

 

[Desdinova]

Thanks guys!

 

[cjbarth]

i have mine set to do both!! Skim surface and bottom intake....I used 1" pvc and a cap for the bottom with holes.....reason for the cap is..if you don't have one...the water will never reach the top(skimmer) portion of the overflow.....now when this is used and I do a simulated power failure, the water stops at the "T" that goes out the back of the tank. Also on the skimmer portion, I use a screen to prevent fry or food from being sucked into the overflow....this plastic screening can be bought at Hobby Lobby (it is Latch hook screen)

 

[David R]

Skim from the top, forget the UGF (especially with digging fish like oscars), keep the substrate shallow, and have enough circulation/flow to keep the waste suspended.

 

[Desdinova]

If I have that much circulation, isn't that going to bother the fish? Oscars like to lay down on the bottom to sleep. I'm imagining them getting spooked a lot, as the circulation pushes them into stuff all night long... I never figured that one out.