excessive current

[dfepeman]

I've recently set up a 39 gal tank (36 x 12 x 20) after having a leaky 45 high tank (same footprint, but hard to reach the bottom to do maintenance). While I was at it, I replaced my old Penguin biowheel filter with a Cascade 1000 canister filter so I could get noise down below in the cabinet. I decided to use the spray bars that come with this filter: they were in two segements and I cut about 2" off each so it would fit across the tank better- as it is now it reaches across ~3/4 of the tank length. My fish (two 6" clown loaches, 6 dwarf blue+black striped cichlids, 4 dwarf yellow cichlids, 16 cardinals, 6 lemon tetras, an otto and a zebra pleco) were not kind to new plants (I suspect the clowns were knocking them around), so I've decided to let the tank establish before I put most of the fish back in. This week I put in the tetras, and the current was just too strong: they all seemed to cower in the corner farthest from the intake, and one by one I got dead or weakened fish plastered onto the intake.

So, I've been looking around for advice on what to do. I can partially close either the intake or exhaust on the Cascade 1000 and get the flow down to 1/2 to 1/3 full, but I've read that this might damage the pump. The Cascade is rated for 240 GPH which means about 8 water changes/hour, and the literature seems to say this is appropriate. If so, why so much current? I wanted the spray bar so I could get some surface agitation, but this is ridiculous!

Could someone advise me on whether restricting the filter flow is kosher (seems wasteful to have a good pump and starve it), or what to do with the intake and the spray bar to minimize the current?

Thanks for any suggestions.

[Michael_Lambert]

I moved your thread here, as you will get better results.. You had orginally posted in a Saltwater forum and i moved it here to the fresh water forum where it should get the results you are looking for.

as for water flow ideally in a saltwater you want to go with 10 times turn over of your total water volume.. as for your tank witch seems to be mainly Cichlids.. i also keep africans and i run a Ehime filter .. running about 10 times turn over, now these fish have no issues with the higher current atleast not that i have seen, But by increasing the flow you are cleaning the water much faster witch i found needed with these fish as they tend to be dirty.

But as for restricting the flow.. i dont see any issues with it.. i have done it to many of my filters..

[Chrismo]

Try making the intake area bigger, it spreads the suction out over a bigger area, making the current less concentrated. The fish will find it easier to resist. You can find attatchments for that if it's a standard pipe size.

I'm not familiar with the Cascade filter, but in general adjusting a pumps gph setting acts the same as increasing head pressure. The pump should be designed to handle it if it's made to go below your tank. But you got word that it does diminish the life of the pump, maybe...

Chris

[dfepeman]

Thanks for the input. I think I'll look into changing the inlet volume a bit. Some posts mention putting a sponge around the inlet, but this would be effectively the same as restricting the inlet valve to the pump; besides, you would need to clean all the junk off the inlet sponge before it ever got to the canister filter.

Another option I've also been thinking about is to drill out the spray bar holes slightly- that should decrease the exit velocity. I notice that I have to keep the water level really close to the outlet holes to get the rigth amount of agitation: too low and I get too much spraying over the top of the surface, and too high I don't get any surface agitation. I guess I am going to have to monitor evaporation more than normal.

I am still not sure if restricting the intake or exhaust valve on a canister filter is better. My gut tells me to restrict the outlet pressure, but I'd rather have experienced folks clue me in.

Again, thanks for yuor suggestions