Fish gasping? at top of water

[jen626 3]

Hi, question about my stepson's pond koi again. 1500 gallon pond with 4 koi ranging from 6-10". The fish have been coming up to the top of the water and it looks like they are taking a breath (I realize that's probably not doing that). It kind of looks like when they come up to eat and take a bite of the food only there's nothing there.  

Ammonia 0

Nitrites 0

Nitrates 5

Ph 7.6

Taken with API freshwater master kit

Temp 62

2 large DIY garbage can filters full of bio balls, plus 2 sponge filters. New cycle, just starting to see nitrates.

Waterfall and air hose for aeration. Prime for dechlor.

Fed API medium koi pellets.

No new fish.

He just added a grid cover to the pond to keep kids and animals out,it has metal poles that go down to the bottom of the pond and a plastic grid at the top. He took the fish out while it was installed. Thanks for any help!

 

[aussieJJDude 122]

Do you have sufficient water agitation? It sounds like you don't have enough dissolved oxygen present...

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[mjfromga 1,785]

Koi need way more oxygen than goldfish. How long do the fish stay there? All my fish do this when I come to the edge of the pond. This is a typical greeting. They're ready for the food. But once I feed them or after a while, they don't do this anymore. 

[shakaho 6,313]

If they do this when you or him come near the pond,  they probably are hoping for a feeding,  as mj said.

What turnover rate in gallons per hour does the pond pump claim?  As a rule of thumb, the pump should turn over 2X the pond volume per hour, in this case 3000 gallons per hour.

He should consider upgrading his food.  That junk contains mainly cereal.  Consider a quality food like this.  Compare the protein content, as well as the price per pound.   The pet store junk food costs several times what you pay for high quality food.