Please comment-- Trickle Filter Design for 150 gal tank

[CKfish]

Hi all,

I'm currently in the design phase for a 150 gallon freshwater plant tank. I want to use a wet-dry filter and am currently designing it. Having never done this before, I've got a few questions that I'm hoping you can help me with. I'm having an acrylic tank made for me, so I need to get the filter design finalized to determine where and how many holes they should drill in it for me. Most importantly, have I overlooked anything?

Design Overview
The filter will be a homemade wet-dry powered by an Eheim 1060 hobby pump. The pump puts out a nominal 600 gph, but closer to 400 gph after you add the 4 foot head pressure. Since the tank will contain between 125 gallons of water, this should result in a turnover of about 3 times per hour.

The current design has a single overflow in the center of the tank. A homemade Durso standpipe will send the water through 1" tubing to the wet-dry unit. Check http://www.rl180reef.com/pages/standpipe/standpipe.htm for the standpipe design, it's pretty slick.

The filter will be constructed from scratch as follows. For mechanical filtration, I purchased a 9" tall plastic unit (about 9" wide and deep, too) that has three plastic drawers. Each of the drawers will have a large number of holes in the bottom to allow high flow, and filter media can be placed in them. This should make cleaning and replacing the mechanical media a snap.

The media drawers will drain into the bio-tower. The "tower" will constructed of 3 paint mixing buckets-- 1 for proper height in the tub, 1 for the filter media (leaning toward Eheim Ehfisubstrat for it's high surface area), and the bottom of the the third for a drip tray. The media drawer unit will be attached into the lid of the top bucket for a leak-reducing fit.

The filter will sit inside a sump comprised of a 24 gallon plastic tub procured from Walmart. I hope to reduce evaporation in the sump by leaving the tub's lid on it and cutting holes to the size I need to run hoses, wires, etc inside it. The sump will house two 250 watt heaters for the tank and eventually a CO2 reactor (yup, we're thinking big on this tank).

The Eheim pump will sit inside the sump with a 3/4" return line heading to the tank. I plan to install a ball valve on the hose to make it easier to remove the pump for maintenance and to reduce the flow rate if it's too high. Inside the tank will be one 'centipede' hose so I can direct the return flow. The centipede will have a couple holes drilled into it as a syphon break.

Questions
1) I understand that you are supposed to have overflow lines with a greater diamter than the return lines, as they will be operating under lower pressure and you need an equal rate of water flow between the overflow and the return. The Eheim has a output of "16/22 mm". I assume this means 16mm interior, 22mm exterior hosing, because Eheim sells a plastic tube diameter with the same specs. Looking at my ruler, this seems to be about 3/4 inches.

If I use a 1 inch overflow tube from the tank to the filter, and a 3/4 inch, will this be sufficient tubing diameter for the rate of flow (400 gph) I'm hoping for? 1" seems to be the biggest I can find, so if not I may need to design for two overflows.

2) Using this setup with a 3/4" return, can I safely install a 'Y' joint and have the return routed to two centipedes instead of one?

3) Am I going to have a problem with the Eheim hose dimensions? Like I said, it looks like 3/4".....

4) Is it a problem if the water level in the sump covers some of the bio-media? I'm somewhat height restricted in my cabinet with 22.5" of vertical space.

5) Did I miss anything?

6) Is there something I should be doing to make my life easier?

Thanks in advance for your BTDT! I'll post an update with photos once it's completed.

CKfish

[MrDaytona]

Hope I can help you with a few answers or suggestions. I have a homemade wet-dry filter beneath my 400 gallon FW and also used the Durso standpipe overflow method.

#1. In following the directions listed in the Durso URL I changed my 1 inch overflow PVC pipe to a 1 1/4 inch PVC pipe which eliminated 98% of the water noise. The cap is drilled with 3/16 hole thus giving me a more of a variable for adjusting the correct amount of air.

#2. I also have a 3/4 return but am not using a centipede. My overflow & returns are within a tower at one end of the tank. What I did find extremely useful was to make the returns extend about 1 1/2 inches above the tower and terminate in an invert "J". (Note: I have two returns - one from the wet-dry and another from an undergravel canister filtering system.) The reason for the higher returns is so I could then have a 1 inch fence on top of my tower to prevent fish and loose plants from getting stranded in the tower and eventually being sucked into the wet-dry filter.

#3. I also have a ball valve on the return line from the wet-dry which I use to regulate the return from my 1200 GPH pump. So far I haven't seen the need for a heater as my lighting and the room temperature does a more then adequate job.

#4. My water level in the wet-dry is usually covering the bottom inch of bio-balls. Whether this is good, bad, or even critical I have no idea!!!!
My main concern, so far, is that when the wet-dry is shut off that the enclosure will hold all the water that eventually settles in the wet-dry. By drilling 1/16th holes in the return line I also break the siphon action.

Best of luck and I hope this has helped somewhat!

[CKfish]

Thanks for the response.

I ended up ordering a slightly larger pump. I'll use the ball valve on the return to keep the flow down, so I figured it'd be better to go oversize on the capacity rather than having to upgrade later. Hopefully with only 400 gph the 1" drain will suffice. If you're putting 1200 gph through 1 1/4" it sounds like it should.

The tank is on order right now, so I'm currently building the stand. Once it arrives the filter goes together and I'll post an update.

Thanks again!

CKfish

[MrDaytona]

CKfish - To reiterate - I have a wet/dry system that utilizes a 1200 gph pump and while the return line is a 1 inch that necks down to 3/4 inch - the Durso overflow standpipe is 1 1/4 inch as recommended at the URL you refer to. If you go to the URL and check the section on "Building your own standpipe" you will see what they say about increasing to the minimum of 1 1/4 inch size.

I was originally at 1 inch for the Durso overflow standpipe but the noise was intolerable. When I increased the standpipe to 1 1/4 inches, as they recommended, the noise was eliminated.

You mention you are building the stand. If you plan on having storage and/or the pumps within the stand you might consider having an additional access door on the end rather then just on the larger dimension side. The end door will allow you better access.

Best of Luck!

:P

[CKfish]

Good thoughts, thanks again. I'll post further as I make progress.



CKfish