Sloping sump bottom for easy detritus cleanup

[discocarp]

I've decided on (after much wrangling with different options) a 235g rectangular fiberglass tank for my sump. I almost went with a 300g rubbermaid livestock tub, but I chose the 235 because its square (more space efficient) and because the bottom is flat without ridges, etc to collect detritus where I can't easily clean it out. I'm going bare bottom in both the main tank and the sump.

I'd like to somehow slope the bottom of the tub so detritus collects to one side. This will facilitate easy cleanup. I plan to eventually keep frags in this sump, so the bottom will be difficult to access in most spots. Does anyone have any ideas on what I could do to slope the bottom so that detritus ends up mostly on one side, yet still doesn't collect underneath whatever I decide to use to slope it? I'll definately have some good flow along the bottom to help, but I think my life will be a lot easier if I take advantage of gravity too.

I thought about using acrylic or starboard and sealing it to the side. But 1) I don't know how to seal these plastics to fiberglass (I'm assuming silicone wouldn't work all that well) and 2) What happens underneath the slope? I don't want water stagnating under there, and air trapped underwater seems to be unwise.

I also thought about putting in several sheets of starboard across most of the bottom, leaving a depression along one easily accessible side, and sealing it in. This way the water flow would hopefully move the detritus around until it collected at the low point of the depression. This seems reasonable to me, but I have no idea how it might actually work out.

Any advice is appreciated.

Peter

[ChasingPuck]

Not sure if I am picturing this correctly, but it sounds like you'll end up with contact points along the middle? If so, solid waste will collect there. A couple options I think might work, depending on the depth and such. Use eggcrate and PVC to build a shelf that is level, while the sump leans, and have about 2-4 inches gap ont he low side for easy access. Or, put a pre-filter on to catch solids before they hit the sump, and make sure there are detrivores that can access the prefliter to clean it.

[discocarp]

I considered leaning the sump, but I'm concerned about the structural integrity if its leaned. All the weight would be focused at the joint between the bottom and side.

The prefilter is my backup plan, I was thinking about using cheap, easily replaced floss on the return from the tank and changing it out very regularly. This would help, as long as I changed it out regularly, but I don't think it would catch it all.

I'm not sure where the contact points will be exactly. The idea is to get the detritus to collect in the front or side so I can siphon it out nice and easy.

Peter

[MadTownMax]

how rigid are the sides? I'm betting w/ fiber glass you'll get some flexing, so whatever you have making that slope will need to be wider than the dimensions of the tank, otherwise you'll have gaps on the sides. why not some bottom-up baffles (maybe just 1 or 2, that collect most of the detritus?

[discocarp]

Baffles are a really good idea that I hadn't even considered. Keep in mind that with frags and some rock in the sump, not all the detritus will be coming from the main tank (although I believe most will). But perhaps with some baffles and a lot of flow in the sump it will work out.. Thanks.

Peter

[MadTownMax]

baffles are simple and effective. These are not "bubble traps" though, you will want a design more like those used by waste processing plants, using baffles coming from the bottom of the tank, with short ones first, then taller and taller (depending on how many you want) if you would like to incorporate this w/ your slope design, glue some acrylic "slopes" between each baffle (sloping perpendicular to baffles), so you can remove detritus from one side of your tank. Of course you will still have to compensate for some "bowing" of the tank.

If you do decide to go with a simple slope design though, how about setting your sump at the angle of your desired slope and pouring in some concrete, let it set, then epoxy-paint seal it. Of course it might weigh a ton, depending on how high of a slope you might want, but it will get the job done, and there won't be anyplace for stagnant water.

[Agu]

Peter,

I think you're trying to solve a problem that doesn't exist. Sure you'll get some detritus down there, but you'll also end up with critters that will process the waste. I'd say use a turkey baster or powerhead to periodically stir up the detritus and have a temporary filter on your return pump intake when you do this.

Another alternative is to make a stand out of eggcrate and pvc (make sure water can flow through the pvc so it doesn't become stagnant) and raise everything a couple inches off the bottom of the sump.

jmo,

Agu

[brentp]

Originally posted by Agu

I think you're trying to solve a problem that doesn't exist. Sure you'll get some detritus down there, but you'll also end up with critters that will process the waste.

The critters help a little, but they also create waste...
I think getting the detritus out by the methods posted earlier in this thread should work well. Hopefully I'll be setting up a 120 gallon system in the next few months and have been thinking about how to build my sump. I think the baffles with some acrylic glued at the bottom at an angle may be a good idea. Thanks for the ideas!