How many fish?

[Ruthie]

I am new here and I have a very basic question.  How many fish can a garden pond support?  In a healthy manner, of course.  How many is overstocking?  I have seen answers like one koi for every 100 gallons or one koi for every 5 gallons. 

I am new to ponding.  We installed our pond a few months ago.  It is 13 x 10 with a maximum depth of three feet, but with plant shelves...if I calculate it with an average depth of two feet it comes out to something like 1700 gallons. I have enough pumping power to turn over the water volume each hour or hour and a half, but we want to add some other water features, so this will increase as soon as I can get an electrician out here.  Our filtering system is a biofilter contained inside our barrel fountain which spills into a 200 gallon bog/gravel filter which then trickles out over a lava rock layer before returning to the pond.  We are low tech and I constructed all the filters myself.  We have plantings of Louisiana iris, pickerel, hyacinth, water lettuce, water primrose, sedges, etc inside the pond itself.   So far, the water is clear and balanced...I tested it. 

Currently, we have about 15 fish...comets, shubunkins and one koi who have all tripled in size since they were purchased.  We also have an abundance of mosquito fish and a helathy population of grass shrimp. We have a big invasion of tadpoles not long ago and now we are inundated with baby frogs everywhere.  Pretty cool!

I am hoping to add two more koi.  (Though courtesy of this forum, I am intrigued by the wakins  )

But can anyone give me a good rule of thumb to avoid overstocking?  How many is too many?  My aunt has a pond and is asking me to please take some of her babies.  Or do I already have enough fish in there?

Thanks so much.

[miguynmkoi]

Welcome!! 

I'm no expert and also rely on AP know-how.  What is a grass shrimp ?  Your pond sounds wonderful....pictures coming soon? 

[Bonnie]

Hello there and welcome to American Ponders!

According to my calculating, you have approx 1,900 G.


A safe estimation is one inch of fish for every square foot of surface area.

You want to remember that fish will grow, so calculate their maximum size........

[Lynda]

For koi the rule of thumb is generally 250-500 gallons per fish is minimum.  When they're small you can get away with more fish in less water, but koi will grow regardless of their conditions (perhaps not at their potential but they'll grow) and an overstocked pond is just a disaster waiting to happen.  Goldfish, I don't know; but koi, that's my passion.

[Ruthie]

The grass shrimp are native to our area...I snatched some from my dad's stocked bass pond.  They are small (maybe two inches long) almost clear and are bottom scavengers and grazers.  I assume the fish snack on the small ones.


This is what they look like.  I have heard them called ghost shrimp, too.

Thanks folks.  I appreciate the responses.  And thanks for the welcome!  I'll find some good pictures of our pond and post them soon.  I am so proud of it

[thepitclub]

Welcome!

Grass shrimp seem like a great pond addition idea. Nice way to supplement the fish's diet! 

Can't wait for pics of the pond! I'm pretty new to the forum also and I have since learned that my pond is

overstocked. I've given away a few large comets and a couple big shubunkins (each about 8 inches+), but I haven't

been able to part with any of my koi.  :'(  But, I'm planning a bigger pond and hoping to accomplish it before my koi

get too much bigger. Maybe if you discover you are going to be overstocked (I was trying to calculate, but I hate

math  ) you could adopt out some of your other fish for the ones you really want. Or, do like the rest of us, and

just build more ponds! 

Also, wakins are goldfish, not koi, and they will not get as big as koi. I have a small one in a tank indoors that I am

waiting to put in the pond until he has grow a bit larger. He's one of my favorites. 

[Julles]

Now, I'm not telling you to be like me, but I CAN tell you that my pond is WAY overstocked.  And everybody seems just fine and healthy.  There are guidelines, but it seems you can get away with a little crowding... things just won't be optimum, as pointed out above.  Besides, admit it everyone, it's so hard to cull out an existing fish, or to resist buying that new one who is just the perfect color and personality.

In my 550 gallon, 7' x 3' x 2.5' deep pond, I have at least 20 fish.  Well, prolly more like 30, but I tend to not count the goldfish and fantails.  You only count the koi, right??       I have a bog filter with a 900gph pump, plus another 700 gph pump operating two fountains.  So it's filtered and aerated well enough. 

But I'm not looking to add anything more; in fact, I would like to cull some out - if I could only bear to part with some. 

But what I think is more important is the balance between all the fish and the ecosystem.  Once everything gets into balance and things are going well, adding some new element could tip the balance and cause a chain reaction of problems, from water quality to fish mortalities.

What kind of two new koi are you looking for?  A certain color or pattern?  Just curious.

[Bonnie]

Jules has another point.. Your fish will eventually spawn and you will have new babies which are hard to cull so you definately do not want to put the maximum amount of fish in your pond now due to it.

Yes alot of us tend to overcrowd but that means that more work is necessary to keep a healthy environment for them.



Jules, please don't tell me that you have 30 KOI plus Goldies in a 550 gallon pond! :'(   

[mascot]

I had heard that the rule of thumb is 250 gallons for each koi, and 100 gallons for each goldie, shubunkin, or wakin.  Most people I have known or have conversed with overstock their pond.  Not all, but most! 

As for koi...well, take a look at the two photos below, the first was taken less than two years ago (when my pond started) and the second was taken recently.  Same koi, more than twice the size - the orange wakin haven't grown much, but you can see the size comparison.  That "shelf" is unchanged, so look at the koi size before and after compared to the size of that shelf, also:





I have three koi and will stop at that.  There are two shubunkins, six wakin and four hifin sharks (bottom feeders that think they are goldfish)

[Ruthie]

I kind of figured that once fish start spawning and you start recognizing them and growing attached, it would be really hard to part with them.  Don't laugh at me, but I have already been thinking about our next pond 

The growth of the koi is amazing.  Our  koi is the biggest of the bunch already.  We purchased two koi after I was certain our water quality was ok.  I have one that is white with black splotches (not sure what that is called, as he has some blue too and sometimes I think I see small bits of orange.)  The other was a tancho.  Well, I lost my tancho to a Bittern.  He got my Sarasa comet (also mostly white with the tancho pattern) and the tancho koi in the course of two afternoons.  I wanted to cry. :'(  Actually, I did cry.    I love the predominantly porcelain white koi, but I have promised myself no more white fish.  Our predator pressure is too high.  We live in a swamp, way out in the boonies.  There are flocks of ibises and egrets and herons in our front yard with each rain storm.  The other day we had a huge flock of roseate spoonbills.  So, this is the long answer I guess...I really don't have a certain koi in mind, only that it has to be one not easily visible from the sky.  I have been shopping a bit, but I have not been able to find one who fits the bill.  And yesterday when I went to the pet store for cat food, I checked the tanks (just to see, of course!) and all of their goldfish and koi looked terrible.  I'll just be patient.  I've done the math, so I am close to my limit without expanding the pond.  Wouldn't hubby just love that 

Blind 'Too...I love that little tuft of grass in the bottom photo.  What plant is that?  it is so pretty!

[mascot]

hi...that tuft of grass...I can't remember what it's called, but I got it at Lowe's with their water plants for about 5 bucks.  It's been there for almost two years and has stayed green.  I'll try to figure out what it is called...unless someone else knows and gets back to you first. 

[Johns]

Ruthie,

The answer to your question is: It depends.  There are lots of variables to take into account, but assuming you want your fish to have the best chance of survival in the event of a power outage (During which your pond aeration and filtration would be inoperative), the most important is surface area.  This is because it is through the water surface that oxygen can enter the water in the absence of waterfalls, venturies, and such.    Fish metabolic processes consume oxygen in the water roughly in proportion to the weight of the fish.   That being the case, the key to fish survival without mechanical aeration is the number of pounds of fish in relation to water surface area.

So, what to do?  The answer is really simple.  Make a list of your fish by length.  For example, 14 fish 4 inches long, 10 fish 8 inches long, 4 fish 14 inches long, and so on.  Armed with this information, go to my FISH LOAD CALCULATOR at http://www.gardenendeavors.com/rack/web17.html and enter the results.  IMPORTANT!  Every category MUST have an entry for the calculator to work.  If you have no fish of a specific length, enter a "zero" for that category.

The calculator estimates fish weight from length and is based on data for standard koi, so other kinds of fish will be off somewhat, but the calculator should still give a "ballpark" result.

[Ruthie]

What a great calculator Johns!  Thank you so much for the link.  I calculated the current load of fish on the pond (very, very low) and then calculated it for when the fish will be full grown.  We are still safe, even if we should have a power outage.  Thank you so much!  I feel better

[Julles]

1.  When you measure a fish, do you include the tail?  meaning, the filmy, transparent part of the tail?

2.  Yes, my pond is overcrowded, but the water is clean, it's well oxygen-ated, and the fish all seem happy.  I do not, however, have plans to buy any more.  (Unless, of course, I find that rare orange / red / gold with black blotches I've been hunting.  )  At some point, I may even cull out some.  There are a couple I don't "like" much, and some that are too dark to see.

2.a.  My fish aren't all that big, and don't seem to grow.  The largest koi is only about 1' from nose to where the tail starts, and he's 5-6 years old.  Perhaps the number of fish in the pond prevent them from growing to full size?

3.  Since koi have such individual personalities, the fewer you have, the better you can enjoy each one.  You know, kind of like having individual "pets" instead of a "herd." 

[frloplady]

In my 550 gallon, 7' x 3' x 2.5' deep pond, I have at least 20 fish.  Well, prolly more like 30, but I tend to not count the goldfish and fantails.  You only count the koi, right??       I have a bog filter with a 900gph pump, plus another 700 gph pump operating two fountains.  So it's filtered and aerated well enough.

I have fewer fish in my 13,000 gallon pond than in your 550 gallon pond.  I figure I'll have about 30 total including little guys in the long run.  25 in there now.

Someone said once imagine having a small house and inviting a whole bunch of people in for a party.  For awhile it's fun, but you can't see everyone..if all the windows were close and the air (water for fish) wasn't keep purified and O2 replenished it wouldn't be comfortable for long.  I watch my koi race around the pond, tag or whatever fishie games they play.  I wouldn't want a lot more in there.

Lots of fish, small pond..high temperatures..power outage......... 

dead fish    Playing roulette..but with fishies lives?  Something will push the pond over the edge eventually. 

1900 gallon pond...  10 koi..and some of those small ones.  Might have to upgrade filtration as they grow, lots of water changes.  New ones may be little now..but they won't stay that way