[WaterLife]

I currently just use powerheads with sponge prefilters on them to not suck any fish or plant matter inside. They work alright, but circulation pumps claim to have a much high flow rate, and they blow a wider current which is nice, rather than a more concentrated outflow from a powerhead.

The extra current would be nice (shouldn't be overwhelming for my fish), so I'm thinking of getting some. Only issue I see is there is no real "prefilter" to keep fish, fry, shrimp or plant matter from getting pulled into the impeller/prop. Is there any safe circulation pump out there, or a way to make them safe?

I do have tons of small fish (1/2"-1 1/2"), plus fry, dwarf shrimp and snails which is why I'm concerned. Some of the grating/guards/cages on the circulation pumps, still have openings/slots large enough for livestock to fit through them.

I think someone mentioned wrapping pantyhose (stocking) around it, but I'm not sure how good that is. Does it clog fast? Does it pull the pantyhose into the propeller? Is the suction still strong and livestock may cling to the circulation pump (just not manged by the propeller, but still stuck against the housing)? Small livestock in a rather large tank (180 gallon), so I was planning on large/powerful circulation pumps.

Circulation pump recommendations?
I guess I'm cheap. Those Hydor Koralias are pricey. I don't mind going for cheap Chinese brands like Aquatop (even though they are cheap, I've still heard they are reliable, strong pumps).

 

[roadmaster]

Well ,with" ton's of small fish,"I would not be too concerned about the few that become chum = more fish food,and fertilizer.
I use a koralia wave maker's on occasion, and have see no great loss in number's of fishes/invert's, but maybe would stick with powerhead's and prefilter's if I could not stand to lose a few.
Can always aim powerhead's at glass or surface to disperse/deflect the flow which makes the flow not so direct.

 

[PlantedRich]

You are kind of fighting to go two different directions at the same time. That means compromise?
I like small several small pumps rather than large for some of the reasons you have. I do a fair amount of breeding and often have small fry but they are not a problem being sucked in. They come with the idea that being sucked into dark spots against their will is not good? It takes a pretty stiff current to suck my fry where they don't want to go. Can't say for shrimp, though.
A large sponge over the intake may work fine and be easy to pull off and rinse?

One way to move lots of water but keep tiny out is to build a cage of something like eggcrate or mod something cheap like the plastic basket strawberries come in. Once you have a cage and cover it tight so tiny can't get close, you can suck lots of water through and not have the cage covering gets stopped up too quickly due to the large surface area. Mattenfilters are really good for this. Massive amount of space for water to go in and one spot for it coming out can make them easier to fit tight.

 

[WaterLife]

Does a circulation pump pull in water from behind the prop (so fish, inverts, plant matter may be pulverized by the prop getting sucked through it)?
Or does the water being propelled forward by the prop, just create a "vacuum" in front of the prop (so nothing actually gets pulled through the prop blades, just gets blown in front, meaning it would be safe from beating/chopping up fish/inverts/plants)?

For those who own a circulation pump, you could simply watch yours in action, whether or not things (debris particulates or loose leaves) get sucked through the protective cage, behind and through the prop/impeller, or if things get swept/pulled/sucked into the current in front of the prop.

 

[jrygel]

Stuff is definitely sucked in the screen from behind the prop.