Scud Safe Pumps

I was trying to create an outline of my future palladium. I'm going for a low tech high efficiency approach, with the whole thing running on one pump. Though it will have a backup pump that only require turning two valves and throwing a switch in case one goes down.

Basically the concern I have is the pump killing any scuds, rotifers, daphnia, etc., that pass through it. I would like to choose a pump that minimizes killing of microfauna but can't find any information on this.

Keeping small organisms from being killed by pumps is more about the filtering layers you have on the intakes for the pumps than on the pumps themselves. If you cover the pump's intake with a four inch cylinder of sponge, then the small water dwellers will have a much easier time of keeping themselves from being sucked in.

Here are some photo examples of the sponge filter system most aquarists find effective:
http://www.fishyrevi...nk001_large.jpg
http://www.discusfis...06/IMG_6860.jpg

Keeping small organisms from being killed by pumps is more about the filtering layers you have on the intakes for the pumps than on the pumps themselves. If you cover the pump's intake with a four inch cylinder of sponge, then the small water dwellers will have a much easier time of keeping themselves from being sucked in.

Here are some photo examples of the sponge filter system most aquarists find effective:
http://www.fishyrevi...nk001_large.jpg
http://www.discusfis...06/IMG_6860.jpg

Those would keep scuds and other strong swimmers/crawlers out, but I would think something like daphnia would wind up stuck to the sponge.

I think MYWAN is looking for a pump that will pass critters with out killing them.

If your current is not real high, then you won't have much trouble with microfauna death. In fact, they are likely to colonize the prefilter, more than compensating for any intake deaths. But don't plan on significant microfaunal populations unless your stock is quite low or you have a refugium or other predator-exclusion area. It's amazing how rapidly a few small fish can annihilate a teeming microcrustacean population.

That's easy: AIR LIFT, provided you're designing it with low head.

Edited by gerald, 18 January 2011 - 04:30 PM.

Rather than reinvent the wheel, take a look at the good ole Magnum. No moving parts come in contact with the water or anything in it. If current is your only goal, no filter media means not only are critter safe, but flow is never reduced by clogging.

When you do use media, you have a built in refugium. In fact I have had mad colonies of scud survive for years in a Magnum in which I never changed the sleeve. Sure, flow was reduced, but the scuds ate enough of the detritus to allow significant flow through. This in a tank full of predators that would never allow scuds to survive.
I've also had huge snail colonies survive inside magnums and even had rainwater killie fry survive and grow inside them.

Most of the centrifigal pumps like Little Giants allow quite large particles to pass through. Again, this assumes you DO NOT use a prefilter. Obviously prefilters will keep critters and everything else out, but then you're a slave to keeping your prefilter clean or clogging steals your flow.

To clarify on my last post, Magnums are actually filters although I suggest the possibility of using them only as pumps [ie without media]. That is probably not cost effective. A standard centrifigal pump is a pump only. You would need to design something along the lines of what marine aquarists call a "wet/dry" filter [assuming you want current and filter to be intergral]. In that case, a syphon overflow typically spills into a sump and the pump returns the clean water to the tank.

What I like about the magnum is the selfcontained, self priming, flood proof design [opposite of sump based wet/dry and varients]. As a primary filter the significant drawback is small media surface and quick clogging. My suggested use is different from the manufacturer suggested. Lots of stuff online to read using what I gave as a jumping off point.

Edited by mikez, 18 January 2011 - 06:06 PM.

It sounds like the magnum might what I need. Could you point me to one so I can look over its design? I'm not that familiar with specific brands or models, only the operational principles on which they work in general.

Here's an outline, subject to change, of the situation. The only prefilter will be where the water exits in the bottom right side of the fishtank in the palladium. Hopefully excluding scuds etc. colonies from passing here. From here the water travels outside the house to a large (bypassable) reservoir. Then goes through the actual pump and return to a planted swamp region (if waterfall is bypassed) on the left side of the aquarium. If the waterfall bypass is turned off it'll pass over the indoor waterfall for increased evaporative cooling and into the planted swamp. It overflows this swamp into a bioball filter which exits into the bottom of the tank on the left side. This keeps the swiftest water near the bottom of the tank with stepped sides to provide low flow (low turbulence) regions for fish that prefer it.

The sources of protected scud (etc.) colonies is the planted swamp, bioball filter, and external reservoir. The reservoir colonies is the main concern in this setup. With the water fall bypassed there will be no significant water level differential. With pumps off the system water level will equalize inside and out, but I need enough head pressure to sometimes operate a waterfall of a couple of feet. If I move the pump to between the prefiltered aquarium exit and the reservoir then, unless the reservoir is bypassed, there is no way to get the head pressure needed to operate the waterfall. Even without the waterfall there is the danger of losing aquarium water level to maintain the water level difference needed to keep the water flow up. I can use a venturi effect to alleviate this but I don't want to make it so complex it's like driving a car from day to day.

Much better if the pump is after the reservoir, with the possibility of a venturi in the reservoir to self regulate the aquarium water level as water is lost to evaporation. The order in which water passes from one region to another is important. The planted swamp needs the CO2 and nutrients from the fish before passing through the biofilter, which is basically a biofilter in its own right. The water then needs to pass through the biofilter before entering the fish tank. The extensive micro/macro fauna colonies is ideally intended to make the food chain self sufficient, at least in principle. Thus I want to minimize damage to these colonies by the pump, the primary concern here being from the reservoir tank.

Maybe not the magnum. You updated your post while I was researching. I want to create an entire experimental ecosystem. So it's as much about the self sufficiency of the indoor ecosystem (including fish) as it is about fish alone.

I don't need the pump to also filter.

Edited by mywan, 18 January 2011 - 07:50 PM.

I believe I have come up with an alternative solution, and far simpler than venturi effects and such.

The water exiting the aquarium is the point at which the planktonic colonies are prefiltered, making it the safest point to add the pump. Rather than then going to the external (bypassable) reservoir simply skip the reservoir altogether in the pump loop. Then add a separate gravity feed line from the reservoir to the tank, with a controllable valve to maintain the aquarium water level. The reservoir can then be maintained with a higher water level, providing for a controlled gravity feed.

This should solve my main concerns, but I still prefer a pump that minimizes damage to microfauna colonies that may get through the prefilter.

Here is a basic outline, subject to change, of the floor view and front view.

Top floor view:


Front view palladium:

After looking at your design an air lift type pump looks good. you can use a one inch stand tube and air-stone inside it to move quite a bit of water. I'm not sure how big your tank is but it looks like you are talking about less than a once or so head. You can move quite a bit of water with a air driven water pump and it doesn't harm fish or crustaceans.

The tank size is about 350 gallons, not counting biofilter, plumbing, and reservoir volumes. As long as the waterfall is bypassed the head pressure is nearly nonexistent. However, the tank is designed to keep turbulence to an absolute minimum while maintaining a very fast water flow near the bottom. This low turbulence is to keep dissolves gas levels as high as possible in the water.

It may seem like a bubbler does not produce significant turbulence, but in fact the physics of bubbles results in a rather extreme 'effective' turbulence. It may not be as extreme as that described in sonoluminescence, but it is more than sufficient to drive the dissolved gas levels down very quickly. I could qualitatively describe the physics of why bubbles do this, same basic reason divers get the bends, when very fast flowing water (laminar flows) does not necessarily, but the point is that bubbles is something I want to avoid. Opting instead for other methods of increasing water surface area.

Even the fast flow region at the bottom of the tank is designed to prevent turbulent flows, and give the fish the choice of what flow rates they are comfortable with in the tank, simply by changing where they hang out. The floor will be contoured to facilitate this flow.