Koi and snails getting sucked into bottom drain

[max384]

I have five koi in the 5-6" range, one 6" shubunkin, five 1-2" shubunkins, and a couple dozen snails. The pond is about 2000 gallons with a 4" bottom drain and a 4280 gph pump. The bottom drain is a Koi Toilet brand drain like this:

But, instead of the top plastic piece, I've got a flat rock on top for aesthetic reasons. There is about a 2-3" gap between the rock and the bottom of the pond. One of the koi in particular seems to enjoy swimming into the bottom drain and getting a ride to my pump box. The first time I found him in the pump box, I got a net and scooped him up and put him back in the pond. I also found about a dozen snails in there that I threw back in the pond. The next day I saw the same koi back in the pump box. When I got the net to go get him, he was gone. I looked in the pond, and saw that he had swam back through the pipe and into the pond through the bottom drain. I then sat and watched him swim into the bottom drain through the pipe and into the pump box and then back a few times. He really seems to enjoy doing this. I've only seen one other fish, my 6" shubby, do this, and only once. Zen Master (yep, I name all my fish) does it all the time though! I'm pretty impressed that he's a strong enough swimmer to do this... But I worry about harming him.

By the way, here's a rough diagram of my pond. There is a pre-filter in the filter box, plus it's a Laguna pump with a grated housing so there is no chance of one of these fish being sucked into the pump itself.

What do you guys think? Is this a problem? Or should I let him keep playing his fun koi games? I also don't mind picking snails out of the filter box once in awhile. I've just been picking them out and tossing them back in every few days when I clean out the pre-filter.

By the way

 

[Dave 54]

Max there should be less than a half inch to allow fish detritus only to go through but not your fish.
o personally I would stop the aesthetic reasoning and set up the bottom drain as its supposed to be otherwise this may well one day end up in tears for you and you'll loose a koi in the process.
We had a bottomdrain cover that kept popping up because we retrofitted the pond I had an orfe regulary make that same journy one day I found that he had jumped cleam out opf the vortex and had died.
To cure this popping up of the cover I found an old traffic cone base , cleaned it up by pressure washing then applied 4 coats of pond paint too it the hole in the middle.
It sits squarly over the bubbler which because the traffic cone base is heavy weighed the bottom drain cover bubbler and all tight agaist the base , there is the less than half inch gap as stated in the AKCA book Koi by Grant Fugjita so no more fish and plenty more detritus .
The traffic cone inadvertantly mirroring the bottomdrain cover he recomends
So to conclude my friend get your swimming togs out your goggles and snorkle and get down there and replace the rock withwat was meant to be there


Dave

 

[max384]

Thanks for the reply Dave!

The way this drain is set up is that you supply the 1/2" diameter PVC pipe and cut to whatever length you want to create the clearance you desire. The instructions recommended 2-3" of clearance, so that's what I went with. The rock on top isn't what is creating the large clearance. I can adjust the clearance while still using the rock rather than the supplied top. Really the only disadvantage to the rock is that debris can settle on top of the rock, whereas the dome is curved, so it is less likely to settle there. Though, I'm plenty okay with this small disadvantage. I actually think there would be much less of a chance of the rock popping off as opposed to the cover, since the rock is far heavier.

I'll definitely be adjusting the gap some time this week to a half inch. In the meantime, I'm putting a cover over the pump box to prevent him from jumping out until I can get to adjusting the bottom drain gap. Thanks for the advice!