Unusual problem with pumps?

16 Dec 2008
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Firstly, a very happy new year to all MASAdonians. May your specific setup thrive and bring you much joy.

Now, here's a little poser to all of you.

I have only recently started my reef tank, which has been running for 4 weeks. I started off on the wrong foot with, shall we say a bad LFS mentor, who I think only saw the short term benefits of selling me the very basic requirements to start-up a 1000 liter reef tank without looking at the bigger long term picture. I was gullible enough to walk into the situation due to not first doing some decent research up front.

So I probably got what I deserved. A beautiful 2 m x 850 x 650 tank in an attractive built-for-purpose cabinet, with only white fluorescent lighting in the canopy, a 1,5 m x 500 mm x 500 mm three-compartment sump, a protein-skimmer , a 2000 l/h return pump and another two in-tank 2000 l/h powerheads. The sand was courser than cat-litter (approx 6 mm granule size) and all this was topped up withtap water and added salt. once all this was up and running for a few days, I did what I should have done beforehand- I started to research the hobby. It led to corrective action, some of which was the subject of a previous number of posts.

To cut a long story short, I now have all the above, minus the tapwater and kittylitter, which was replaced with 1000 liters of cycled NSW and fine aragonite, plus 90 kgs LR (of which approx 30 kgs is in the sump), 2 x Seio M1100 and a Wavemaker in the tank with one of the original powerheads, an external chiller to keep watertemp temp at between 24 and 25 degrees C and fed by the other original 2000 l/h powerhead from the last chamber in the sump and discharging into the first chamberwhich houses 2 x 300W tube heaters. Next, a turf scrubber (lit up at night) splits my first sump chamber in half like a weir (scrubber gravity-fed directly by my tank outlet), then the 30 kgs LR in the second half of the first chamber, the Proteinskimmer in the first half of the second chamber, which flows over a weir into the second half of the second chamber which will shortly become my DSB but currently still houses the original UV set-up, and this then discharges into the third chamber of the sump housing (currently) some fine synthetic filtration matting (approx first half the chamber), followed by the return pump to the chiller, the return pump to the tank (throttled by an in-line valve to balance out the tank level) and finally a phoshate reactor which incorporates a second UV light. Top this up with having changed half the 10000K white light to blue lighing and (still pending, due early new year) a further lighting upgrade by adding 3 x 150 W 20000K MH lamps each with its own 100 mm extractor fan ducted up to an external vent, all suspended above the tank.

Finally, I kept the original hydrometer/thermometer combo originally supplied, but have also invested in a WY 100 refractometer(?) to check salinity, and have also added a test kit which allows me to test pH, NO2, NO3, NH3-NH4, and KH, over and above the Ca, KH, NO3 and phosphate testkit originally supplied by the LFS.

As the NSW was already cycled, I ran the set-up for a week to settle and then gradually began to add soft and hard coral (16 items in total) and finally fish (7 Chromis, 2 x Anthias,2 x "Nemos", 1 x Coral Beauty , 1 x Fox Face, a Prawn Goby, a Cleaner shrimp and a Boxer shrimp and 2 x Turbo snails, mostly Xmas gifts that friends and family rocked up at my home with without much warning. Yes, yes, I know it's a lot of biomass, but cummon,a guy can't look a gift horse in the mouth!

Be that as it may, my tank is now running as follows:
Salinity = 1,025
pH = 8,4
Ca = 500 ppm
KH = 8 dKH
Phos = 0
NO2 = 0 mg/l
NO3 = <1 mg/l
NH3 = <0,01 mg/l
Temperature = 24 degrees C

All the above is pretty much ideal. although I am sure there are bound to be hick-ups along the way. All my LS, except for a solitary piece of LR with 2 x large mushrooms on it which is struggling( it was moved several times to try to find a spot it likes because it doesn't seem to like turbulence at all), are very happy and the corals are all fully open. (photos to follow after 5/01/09 when I get my camera back)

And yet I have a problem of sorts. I have lost 4 fish, all of which have been sucked into the one in-tank Seio M1100 pump inlet. I had some LR scaped around it at first but have removed it as I suspected that it created a kind of "strong suction chamber" from which the fish could not escape once they have entered it. Can this be, or is there another explanation? The chiller installation has been in for only 2 days and the temp used to be around 27,5 degrees C before. Could it have been the high temp that killed them and that they were only sucked in after the fact? If so, why none of the others?

I have also noticed a very ugly, hairy looking grey cretin ( I suspect it is a hermit crab) "skulking" around, and have added an empty shell in the hope that he will inhabit it so I can catch him, but so far he has been evasive. Any ideas or suggestions?

Regards to all!:whistling:


11 Aug 2008
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I reckon the fish were just hiding in the LR and got sucked in. Do not have the rock to close to the powerheads in the tank. And on other powerheads with a suction part sticking out to the bottom, make a plan so that nemmies will not become soup. Some diffuser of sorts, either a sponse or a bigger grid structure thing...
I replaced my suction inlet pipes with 25mm conduit pipe 25cm long drilled with plenty of 5mm holes. And the bottom blocked with a blob of silicone. No more sucking in inmates.


Retired Moderator
29 May 2007
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Cape Town
Hi Baaienaar - your setup sounds great..... BTW: what skimmer did you get in the end? Or are you still saving up for one?

Here's my input: I have 2 x 15000 litre per hour ReSun's, and 3 x SEIO's (2 x M1100's and one M1500) and have NEVER had any fish sucked into the inlet's of any of them......

The only thing I can think of, is that the fish end up being a little bit weak to swim - and are THEN sucked into the pump inlets.... I have never seen this happen to healthy fish...
Another possiblity, is that the fish want to use that specific location where the pump is, as a sleeping area - and that they MIGHT possibly be then sucked into the pump's inlets - while they are sleeping at night (fish are mostly immobile when they sleep).....

Other than that - the fish could already have been on their "way out" due to some illness or perhaps parasite infection...... causing them to become to weak to fight off the currents caused by the pumps....


5 May 2007
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Hi Baaienaar

Sounds like you were off to a shaky start like a lot of reefers that follow the LFS "advice" but that should all come right with the corrective action you have followed.

That is quite a few fish to add at once but are generally smallish fish in a rather big tank so I wouldn't worry about that.

I agree with Jacques that pumps like seios are extremely unlikely to ever be able to suck a fish in. Anemones yes but not fish. I'm sure the fish just got stuck there after dying from something else.

How did you acclimatise the fish when you introduced them?

The ugly cretin sounds like an undesired crab, if it's not already in a shell like a hermit crab then it probably isn't a hermit crab. If you know which rock he is in and it isn't under a pile of other rocks (this is usually the case) then you can remove that rock and try running some RO water over it to try and flush him out.
The other option is to place a bit of shrimp or something in a glass tumbler and then place this at an angle against his rock so he goes in to get the shrimp then can't climb up the glass "slope" and gets trapped.

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