Water temperature question for those with water gardens/small ponds under 2000L/500 gal,

[Criscar]

Good afternoon,

I am thankful to have a place to post my near daily questions! I have been monitoring daily temperature swings in my newly established above ground 300 g main pool (2 ft deep) plus two header pools with bog filters and marginal plants sitting on an overhang all the way around the main pool that will be about 15% of total surface area by themselves but for now half the planters are just getting going. As for floating plants there is also duckweed and loose hornwort that maybe cover another 10%. Definitely nowhere near 60% yet, but will continue to add more and hope for rapid growth on the duckweed and hornwort, along with a dwarf lotus (I know I'll need to manage it to keep it from taking over).

It's a beautiful spring in southern california with sunny days and cool nights, and the water temperature in the main pool is currently swinging about 20 degrees between pre-dawn and late afternoon. Everything I've read about pond temperatures seems to discuss seasonal temperature changes rather than daily changes from day to night. I'd like to add my goldfish to the pond sooner rather than later as they are a bit cramped in the current aquarium (and their poop will only enhance plant growth, no?) but I can't find any info as to how harmful or not daily temperature swings are for goldfish and I don't want to prematurely be forced to shade the pool and inhibit the growth of the marginal and floating plants. Is there any guide or general rule regarding how much daily temperature swings young adult goldfish can safely tolerate, so I know what I'm aiming for, or is this an info-free zone?

 

[mrsclem]

You are concerned about the daily temp changes in the pond? It's not a concern at all, goldfish are tough as are most pond fish. The problem with temperature difference is moving a fish from lets say an aquarium at 82° to a pond that is 50°. As you are in California, keeping the water cooler in the summer is the issue but with plants shading it, you will be fine. I find I sometimes have to add some tap water in late summer if my pond gets over 85°.

 

[Criscar]

You are concerned about the daily temp changes in the pond? It's not a concern at all, goldfish are tough as are most pond fish. The problem with temperature difference is moving a fish from lets say an aquarium at 82° to a pond that is 50°. As you are in California, keeping the water cooler in the summer is the issue but with plants shading it, you will be fine. I find I sometimes have to add some tap water in late summer if my pond gets over 85°.

that's good to hear. It's literally not mentioned anywhere so I couldn't figure out if it's not mentioned because it's never an issue vs it's not mentioned because larger ponds don't have the same amount of daily temperature swings as very small ponds

 

[brokensword]

that's good to hear. It's literally not mentioned anywhere so I couldn't figure out if it's not mentioned because it's never an issue vs it's not mentioned because larger ponds don't have the same amount of daily temperature swings as very small ponds

are you saying, though, that your WATER temp is swinging 20 degrees, or the air? If water, that kind of change can affect the health of your fish for sure. As mrsclem said, you can add the fish if you do it very slowly, but unless you have a dire reason, were they mine, I'd wait until the water temp difference is within 10 deg. Water won't change as fast as air but with such a small amount of water in your pond, it'll probably happen more than you want. If you can, and for future usage, I'd cover with some sort of ag plastic sheeting so you don't get such fluctuations. I do this for my pond and it's considerably larger. The benefits are minimal temp swings, less evap during winter/cold/windy months, and it also keeps debris out of the pond during this time.

 

[Criscar]

are you saying, though, that your WATER temp is swinging 20 degrees, or the air? If water, that kind of change can affect the health of your fish for sure. As mrsclem said, you can add the fish if you do it very slowly, but unless you have a dire reason, were they mine, I'd wait until the water temp difference is within 10 deg. Water won't change as fast as air but with such a small amount of water in your pond, it'll probably happen more than you want. If you can, and for future usage, I'd cover with some sort of ag plastic sheeting so you don't get such fluctuations. I do this for my pond and it's considerably larger. The benefits are minimal temp swings, less evap during winter/cold/windy months, and it also keeps debris out of the pond during this time.

It is the water temperature I am talking about, not the air temperature, and I had thought that mrsclem was also talking about daily water temperature changes?

For example, just before dawn this morning the water temp in the pool was 56 degrees. By late afternoon today, it was 74 degrees. If it's relevant the air temperature had an unusually big swing for our area from about 51-77 the past couple days. I assume you are suggesting the sheeting to hold in heat at night? I was planning on using a thick underlayment as a blanket over the pond in the winter at night, but had not been thinking this would be necessary year round. It's only for about 1 month in spring and fall that we get temp swings here, otherwise the average daily and night temps are usually less than 20 degrees apart here in coastal southern California. I am hoping that with the plants growing in, they will help prevent excessive heating of the pond in the summer by the time we actually get hot-ish weather (usually no sustained hot weather until mid-July or so).

I'm not transferring them for at least 2-3 weeks in any case, so hopefully the weather will have settled down a bit by then.

How much of a daily change in temp does your pond have from low to high in spring?

 

[brokensword]

It is the water temperature I am talking about, not the air temperature, and I had thought that mrsclem was also talking about daily water temperature changes?

For example, just before dawn this morning the water temp in the pool was 56 degrees. By late afternoon today, it was 74 degrees. If it's relevant the air temperature had an unusually big swing for our area from about 51-77 the past couple days. I assume you are suggesting the sheeting to hold in heat at night? I was planning on using a thick underlayment as a blanket over the pond in the winter at night, but had not been thinking this would be necessary year round. It's only for about 1 month in spring and fall that we get temp swings here, otherwise the average daily and night temps are usually less than 20 degrees apart here in coastal southern California. I am hoping that with the plants growing in, they will help prevent excessive heating of the pond in the summer by the time we actually get hot-ish weather (usually no sustained hot weather until mid-July or so).

I'm not transferring them for at least 2-3 weeks in any case, so hopefully the weather will have settled down a bit by then.

How much of a daily change in temp does your pond have from low to high in spring?

that's a pretty large water temp swing in one day. Goldfish are tough but coming out of winter, they're most vulnerable. Now, maybe in Cali you don't get such cold that they hibernate much and are less susceptible. It's because you have only the 300 gallons. My pond is 7k gallons and I've been monitoring with temp guages both air and water the past month, month and a half. When the sun was shining and the pond tent was up, the temps would rise maybe 3 deg F while the air above (and inside the tent) would rise 15 or so (I had some small holes that was letting outside air in and out). This was when outside temps were below freezing and going up as high as 35. Later on, the outside air was rising to mid 50s and the water temp rose as much as 5 deg while the air under the tent went up 20 deg or so. My point though is the small rise also meant an equally or even smaller drop at night. So, temp swings were no more than 5 deg or so and I could see from my underwater cam, the effects on the fish when the water temp was below 50. Over that number and their behavior wasn't nearly as affected.

Currently, air temps with the pond tent down are ranging from mid 30s at night to as high as 70s yesterday during the day. Pond water has ranged ranged from 49 to 58. With the tent down, the water WILL cool quicker but still not that fast simply because I have so much. Some greenhouses even use vats of stored water on their northern wall as heat wells for night time temp regulation.

I'm in Michigan though and we have temps during the winter of sub zero some times, though this winter we only had one or two weeks of sub 10 deg, a milder winter for sure. It is a lot easier to keep a large pond than a small, as you're probably finding out, simply because changes don't happen as quickly (which is a danger for the fish) and you have a lot of latitude to make mistakes and fix them in time.

Perhaps LPS is in your future? (Larger Pond Syndrome)

If it were my small pond, I'd definitely figure a way to keep the temp swings from being that drastic, just to help the fish transition. One advantage you have that I don't with the smaller pond is that putting up a pond tent would be super simple and pretty cheap. You could just make a temp tent from pvc and plastic sheeting weighed down on all sides with the pvc being your tent poles. Realize, if you do go this route, that pvc gasses off and it can hurt your plastic, be it regular or agricultural. Best bet here is to paint your pvc; that'll stop the UV degradation to the poles and if you get ag plastic (mine came from Cali, so..), it'll be UV resistant and last at least 7 years at 6 mil.

 

[Criscar]

that's a pretty large water temp swing in one day. Goldfish are tough but coming out of winter, they're most vulnerable. Now, maybe in Cali you don't get such cold that they hibernate much and are less susceptible. It's because you have only the 300 gallons. My pond is 7k gallons and I've been monitoring with temp guages both air and water the past month, month and a half. When the sun was shining and the pond tent was up, the temps would rise maybe 3 deg F while the air above (and inside the tent) would rise 15 or so (I had some small holes that was letting outside air in and out). This was when outside temps were below freezing and going up as high as 35. Later on, the outside air was rising to mid 50s and the water temp rose as much as 5 deg while the air under the tent went up 20 deg or so. My point though is the small rise also meant an equally or even smaller drop at night. So, temp swings were no more than 5 deg or so and I could see from my underwater cam, the effects on the fish when the water temp was below 50. Over that number and their behavior wasn't nearly as affected.

Currently, air temps with the pond tent down are ranging from mid 30s at night to as high as 70s yesterday during the day. Pond water has ranged ranged from 49 to 58. With the tent down, the water WILL cool quicker but still not that fast simply because I have so much. Some greenhouses even use vats of stored water on their northern wall as heat wells for night time temp regulation.

I'm in Michigan though and we have temps during the winter of sub zero some times, though this winter we only had one or two weeks of sub 10 deg, a milder winter for sure. It is a lot easier to keep a large pond than a small, as you're probably finding out, simply because changes don't happen as quickly (which is a danger for the fish) and you have a lot of latitude to make mistakes and fix them in time.

Perhaps LPS is in your future? (Larger Pond Syndrome)

If it were my small pond, I'd definitely figure a way to keep the temp swings from being that drastic, just to help the fish transition. One advantage you have that I don't with the smaller pond is that putting up a pond tent would be super simple and pretty cheap. You could just make a temp tent from pvc and plastic sheeting weighed down on all sides with the pvc being your tent poles. Realize, if you do go this route, that pvc gasses off and it can hurt your plastic, be it regular or agricultural. Best bet here is to paint your pvc; that'll stop the UV degradation to the poles and if you get ag plastic (mine came from Cali, so..), it'll be UV resistant and last at least 7 years at 6 mil.

My fish will be coming from an aquarium, so they haven't had any overwintering or hibernation to deal with prior to this. We are also fortunate that there's only one month of the year where the average low in my area is below 50 degrees, and that's december, when the average low is 47 degrees. Hence the high real estate prices that severely curb my developing LPS

 

[Lisak1]

You have 500 gallons of water that's swinging 20 degrees in a matter of hours? Is this an above ground pond? Are you measuring the temperature near the top or the bottom? Because that's almost impossible to believe. Not saying you're wrong, but that "unusually large swing" you mentioned is defined as "spring" here. We can go from 80 in the day to 40 at night, and in fact today probably will. Pond temp is just slowly climbing and with just a day or two of that will only gain a few degrees. Once it starts rising in the spring it never goes backwards. And while I do have a much larger pond that's in-ground, water generally behaves the same everywhere.

 

[Criscar]

You have 500 gallons of water that's swinging 20 degrees in a matter of hours? Is this an above ground pond? Are you measuring the temperature near the top or the bottom? Because that's almost impossible to believe. Not saying you're wrong, but that "unusually large swing" you mentioned is defined as "spring" here. We can go from 80 in the day to 40 at night, and in fact today probably will. Pond temp is just slowly climbing and with just a day or two of that will only gain a few degrees. Once it starts rising in the spring it never goes backwards. And while I do have a much larger pond that's in-ground, water generally behaves the same everywhere.

as per my original post, it's a newly set up above ground 300 gallon main pool (it is a rubbermaid stock tank, which I did not mention above) with as of yet inadequate shade cover from the new plants as those are still growing in, and these swings occurred between pre-dawn and late afternoon on days where the air temperature highs and lows varied by close to 30 degrees. A couple days after this post the weather settled down in my area to it's more typical 10-15 degree high/low swings and the temps in the pond have settled down to 6-9 degree swings. Plants are also growing speedily so I imagine within a month or two this won't be much of an issue.

I would imagine anyone with a large in ground pond would not experience this issue, so that is why I was hoping to hear from others who also have small and/or above ground ponds, since it seems like this would specifically be a small pond/water garden issue and not an issue for those folks with an enormous pond. I'd love to have an enormous pond but that's simply not possible where I live unless you want to give me $1.5-2 million dollars to move to a larger property in my area

 

[brokensword]

as per my original post, it's a newly set up above ground 300 gallon main pool (it is a rubbermaid stock tank, which I did not mention above) with as of yet inadequate shade cover from the new plants as those are still growing in, and these swings occurred between pre-dawn and late afternoon on days where the air temperature highs and lows varied by close to 30 degrees. A couple days after this post the weather settled down in my area to it's more typical 10-15 degree high/low swings and the temps in the pond have settled down to 6-9 degree swings. Plants are also growing speedily so I imagine within a month or two this won't be much of an issue.

I would imagine anyone with a large in ground pond would not experience this issue, so that is why I was hoping to hear from others who also have small and/or above ground ponds, since it seems like this would specifically be a small pond/water garden issue and not an issue for those folks with an enormous pond. I'd love to have an enormous pond but that's simply not possible where I live unless you want to give me $1.5-2 million dollars to move to a larger property in my area

me and Lisa will start a go-fund-me for ya! Course, it may take a while!

 

[islandboy]

(it is a rubbermaid stock tank, which I did not mention above)

Is it black? Would draping the sides with something lighter help reduce the temperature swings?

 

[WaterGardener]

Could you put a shade sail over it? We use them every year and they don't hamper the growth of plants, but they do keep the water cooler.

 

[Criscar]

Could you put a shade sail over it? We use them every year and they don't hamper the growth of plants, but they do keep the water cooler.

Thanks! I did end up buying a partial shading net for when it's hotter this summer just in case but the weather here settled down and I don't need it right now. Is your shade sail rated to allow a certain amount of light through?

 

[Criscar]

Is it black? Would draping the sides with something lighter help reduce the temperature swings?

Thanks for the idea! It is black. I did an experiment with a smaller tub made out of a similar material recently and covered the rim and any exposed above water areas with tinfoil and surprisingly, it really didn't make much of a difference in the smaller tub. Fortunately the temps settled down here and it hasn't been an issue and by the time we start getting actual warm weather here (usually July) the plants will have grown in to cover most of the rim (lots of creeping jenny to the rescue).