Tank overflow?

[enchanted]

I was at my LFS today looking at 125 Gallon tanks. At $369.00 he was a few cents cheaper than petsmart but it had these funky looking half circular pieces on the back. So I asked and was told they are overflows that are primarily used for Saltwater tanks, but can be used for FreshWater tanks.

I should of asked more, but then he said that without the overflow the tank is 70-80 less!

Alright, so what is the purpose of these and what do they do? And why in the world are a couple of half-circular plastic pieces costing $70-80?

 

[konrad05]

It's if you're going to use a wet-dry filter system and most likely a sump underneath the tank. It's like a giant filter that you don't have to clean too often, and I think it's fairly easy too. You basically have a tank underneath that the water pours into, through filter, then gets pumped back into the tank. Only thing I always wondered was if you had to do the calculations of the height of the tank/water level to find the gravitational pull and calculate how fast the water is coming into the sump to match the speed of the pump/powerhead so that the sump doesn't overflow or go dry

 

[enchanted]

It came move any slower than the smallest hose you fit on it nore faster than the biggest hose.

But I now understand it. I did before, just didn't know all the terms. I'm not sure if that would be good for a well planted tank or not.

 

[tsr770]

Usually tanks with overflows are rated at a certian flow rate, like maybe 700 gph, so you will need a return pump that is somewhere close to that number and you would be fine. A overflow will only dump out as much water as what is returned by the pump in your sump, which is what keeps it from overflowing the tank, or the sump.

If I was going to buy that size of tank I would get one with overflows and cap the bulkhead fittings and use a normal filter system in it, already having the overflows in place would always leave the option of setting up a full on reef tank in the future.

 

[enchanted]

That is something I would like to eventually do, but right now I'm getting my "fins" wet with Freshwater and planted tanks.

I'm looking at this for a replacement for my 55 Gallon Community tank, but I like the idea of having my options open.

 

[andywg]

Just to add my views on this...

If the tank comes with overflows I'd use it (provided you can stomach the expense of the pipe, and sump and that).

I'm setting up my 85 gallon freshwater with two sump tanks, one is a home made filter (with 15 gallon capacity!) and the other is mostly planted to allow nitrate removal.

It's proving a pain to set-up but once it is I know it'll look fine (all heaters and stuff are in the sump, not the tank).

The only problem with overflows is making sure the siphon can be kept and restarted (otherwise you may find the water goes on holiday to your floor...) but this shouldn't be a problem with newer ones.

And as previously mentioned it can easily be transformed for reefkeeping.

You might want to watch for noise though, it s not unkown for the overflow's to gurgle without some modifications.

----------------------------

edit: As far as my understanding goes, so long as the overflows are setup right the flow rate is decided by the sump return pump until the maximum rated flow rate for the boxes (at which point you begin to dry the sump and flood the display tank).

HTH
Andy

 

[Lateral Line]

>>> but then he said that without the overflow the tank is 70-80 less!

So get it without and spend the saved money on a decent external canister filter. I have had overflow tanks, but don't any more.

 

[tsr770]

The only problem with overflows is making sure the siphon can be kept and restarted (otherwise you may find the water goes on holiday to your floor...) but this shouldn't be a problem with newer ones.

With a in-tank overflow there is no worry about the siphon being maintained as the water goes thru wiers at the top and as long as you have a proper sized sump nothing should ever overflow if the return pump stops.


LL makes a good point too, but you say that maybe one day you would like to go SW, and that would be my decider on spending the extra cash up front. I have went thru the hassle of finding someone willing to drill a tank, building a wier setup and getting a standpipe set up correctly, and to me the 80 dollars more up front would be worth it to me.

I suppose it is a decision you will have to make when figureing up a budget for the tank and go from there.