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More Mini-pond Considerations and Guppy Issues


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A while back I started this thread about starting a mini-pond, a ~50 gallon kidney bean partially buried pond liner... 

Since then I have used some crushed coral and flora max for substrate, sponge filter and more recently an 8" waterfall which I dumped some bio balls and more sponge to since it had a trough and why not. I also added a 200 watt heater to help prop the temp up which does help but still not quite warm enough to add any live stock. I think a few more week things should be ready. My plan is to put some guppies in the pond, if I can find enough cover for them. Having a hard time finding stuff like hornwort and a tad early for pond plants but I do have a couple lily pads started. 


I have a 20 gallon tank setup inside. Our well water is on the softer side, so I opted to use crushed coral in the 20 gallon tank as well as the mini-pond. The 20 gallon tank is sitting at 7.8 and the pond a little higher (evaporation?) at 8.2. The 20 gallon is a newly cycled and since i have been running medication and having to change some of the water the water is a little cloudy. No ammonia/nitrite and nitrates less than 5 ppm (down from 40 after it finished cycling on 3/9). I did make a mistake and bought 4 guppies from a well known chain store to which 3 of the 4 guppies died in less than 48 hours. So I did get 8 more guppies from a local pet store and did not have quite as bad luck, I've lost 1 or 2, but I do have one that is behaving weird. In the attached photos the guppy will lie on the bottom of the tank and then swim off, but I have not seen it swim more than halfway up. I can't see anything visually wrong and the rest of the fish seem to be fine. (seems the photos aren't rotated correctly). I have treated the tank with Maracyn, Para cleanse and Ich-X.


The consensus of responses I got from other sources are that guppies aren't as hardy as they used to be and that I just got a bad batch of guppies, etc. Not entirely sure that is true, I just think getting them from a chain store and a newly cycled tank that I'm running meds through probably is part of the equation. My question about the guppies since I have not previously kept guppies before are things to look out for, or other "general" tips.

Someone suggested brackish water. Which is also something I haven't had experience with. I did lookup to get an idea of how much salt I would need to add for brackish water...in short depending on whether you go "low end" or "high end" brackish, closer to marine, it seems you would add somewhere around 1.5 lbs of marine salt for a 20 gallon tank. The two concerns I have is whether any plants can acclimate to brackish water that have previously been in freshwater and since my plan is to keep guppies in an outdoor pond, I don't know how difficult it would be to maintain brackish water outdoors or that there is a whole lot of benefit of keeping guppies in brackish water. Definitely would prefer the easier route but if brackish water is a hands-down good way to go for guppies and the plants won't die off it is something I would look at doing. Plants I plan on keeping in the 20 gallon are really going to be limited to floating plants like duckweed, frogbit and water sprite...hornwort if I can ever find any. Some sources suggest these plants will tolerate brackish water but I am a bit skeptical. Plants I plan on keeping in the mini-pond are the same as the 20 gallon plus lily pads and other pond plants like water hyacinth, water lettuce and so forth. 

Getting to some of the concerns about the pond itself. One of the concerns I have is temperature. I have been monitoring the temps for some time and I am worried that when the hot weather arrives that I will have a hard time keeping the temp at or under 82 F. The pond will be in sunlight between 11 AM and 3 PM which is enough to warm up the water quite a bit and it hasn't been very warm or humid yet. I don't know if having a lot of floating plants covering the water surface will help enough to keep the temp under control or not. Can't really move the pond at this point, not many places get less sunlight that is level enough to keep the pond. 

Any suggestions and advice are welcomed 🙂



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I've had this happen to my guppies, it might be camalanus worms although I wouldn't say that is the problem right away. You could try feeding them some frozen food or live foods to get it fattened up, it might just be week from not being fed enough. Guppies like the warmer temperatures, I don't think they will mind the 82 degree temperature, sure, they might end up dying faster but they will pump out the fry faster too. Good luck with your pond!

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  • 2 weeks later...

So the good news is the one guppy that was acting strange seems to be fine now almost right after my last post.

A couple of strange things about the pond. The pH has up until recently been around 7.8-8.0, now is getting up in the 8.3-8.4 range, still nothing to write home about and thought it was simply due to evaporation. Except rain and topping it off hasn't had much effect. I do have both crushed coral and some floramax planted substrate, it's about half and half with the crushed coral kind of on top, some of it did get mixed. I suspect it is the flora max because I thought crushed coral would only take the pH to a certain point...

The water parameters recently...


I've added enough ammonium chloride to cycle a 150 gallon tank, the mini-pond is around 50 gallons. I will see a small amount of ammonia, a small amount of nitrite and never have got nitrates to appear. I thought maybe algae is taking care of it but the water has only recently turned green and added plants recently. Does the sun have an effect on things? I'm just surprised that the nitrates didn't go through the roof. We did have a lot of rain in March but not so much this month so not a lot of water has overflowed out of the pond. 

Finally, one of my other concerns is temps. Hasn't got hot yet and the pond hasn't got above 75 as far as I know. I miss out on peak heating at work so it may have gone 1-2 degrees more. I am wondering once we start getting 85...90+ days that the pond will far exceed the 82 degrees. Not sure how well or if guppies will tolerate temps going well beyond 82 F during the afternoon. 

To give a better description of the weather we typically get in Western NC during the summer, it's humid (60-70's dewpoints) and temps typically don't exceed lower to mid 90's, overnight temps in the lower 70's. Afternoon thunderstorms are fairly regular but not always daily, but often will cool things down even if it doesn't rain. Starts drying up in August and remains hot until mid September. I expect to be able to keep guppies outside until the end of October (depending on weather).

That being said I have recorded the pond temps periodically. There is a 200 watt heater set at 72 to help prop the temps up.


I know major nermage with the Excel spreadsheets....

Seems the temps range +/- 15-20 degrees on a sunny day right now. I think once the humidity starts staying high, when we start staying 65-70 overnight with matching dewpoints the range will be a little less. I'm wondering if I will end up needing more shade or more plants to cover the top of the pond. The pond gets about 5-6 hours of sunlight, from about 10:30 to about 3:30 roughly.

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