Marineland 300 DD Overflows

[kris101]

I just got a 300 DD and have plans to make it a peninsula. I was considering cutting out one of the over flows and run the tank on one overflow that will be in the back corner.

Will one Overflow be enough? Drain and return

Would using both holes as drains even be enough?

I have heard the MarineLand Overflows are not good anyway so I was also considering a glass holes 1500 kit, but if I can get by with one original over flow that would be ideal.

Any suggestions?

 

[ca1ore]

From a mechanical perspective, it depends a bit on how much water you plan to push through the sump. At the very least you would want to use both overflow holes as drains. Let's say you decided to go with 1,000 gph though the sump, and set the drains up as a Herbie. The siphon side would handle that flow without any issues, but should the siphon get completely blocked (unlikely but possible) the backup would struggle to keep up. The other issue is whether only a single overflow would give you adequate surface skimming.

Not sure if the 300DD comes non RR, or maybe you have the tank already, but setup as a peninsula, it would make more sense to have an overflow that runs the entire 24" width of the tank on one end.

 

[dave.m]

+1 - A coast-to-coast overflow at one end is the best idea for a peninsula arrangement.

Dave.M

 

[kris101]

I already have the tank.. I was looking at the Glass holes 1500 GPH kit and have heard good things about them. Its not coast to coast but I can't see how that kit would increase the skimming area over the MarineLand overflow

I always estimated that a 1" hole can handle 750 GPH. Since it has 2 1" holes I was hoping it would be enough. I would like to at least get the tank turned over 3 to 4 times a hour. I tend to not want to run a high speed sump but I wonder if turning over the volume 3 times a hour is efficient enough

 

[dave.m]

I usually aim for 5x tank volume turnover per hour. That would be 1500 gal/hr for a 300 DD tank, requiring a pipe 1.6" in diameter (per RC's Reef Calculator) or two 1" drains.

Dave.M

 

[kris101]

So that leave the question will the single MarineLand over flow work with 2 1" holes? In theory it should

 

[hobbzz]

No it will not. Not pushing that kind of flow. The slits are far too narrow to allow that much water through, without the water level rising in the tank and touching the braces. I have about 700gph total running through both overflows, and I just took a dremel to the slits to widen them last week. Otherwise the braces dip into the water.





I actually widened them up a lot more after taking these pics.

What might work is if you removed all of the slits and replaced them with gutter guard. But you would very likely also have to shave down the top of the overflow to make the edge that the water flows over lower. But if you lowered it too much, you would run the risk of seeing the water line below the trim.

 

[kris101]

I did dremel out the overflow already. The more I research this the more it looks like I will be ordering a 1500gph kit from gl*******s. I'll have to drill 2 holes on the side the but as small as the Glass holes skimmer box is, I have a hard time believing that it can move more water than Marineland overflow

 

[ca1ore]

It's more the size of the bulkheads that determine the volume of water an overflow will handle. Also, the ML corner overflow only has about 10 linear inches of actual overflow - less than the gl-holes one does.

 

[hobbzz]

The bulkheads are one thing, the overflow is another. Since DD tanks are known for the braces dipping into the water if you try to push too much water through the small teeth in the overflow, I thought he was referring to that. In the case of DD tanks, the bulkheads can handle way more flow than the overflow teeth will allow through.

The stock overflows are horrible for surface skimming. I wouldn't want to go with something that has them than both of them combined. As far as using both for bulkheads for drains, I agree with ca1ore that it would be risky with no emergency drain. I would definitely use the bulk reef supply strainers if you went that route.

 

[kris101]

Looks like I am going to order the 1500 GPH overflow kit from Glass holes. I was really hoping to get by using 1 ML overflow. With a tank this big I might as well do it right from the beginning instead of wishing I did 6 months from now.