Stock tank in an unheated greenhouse

kkirkt

Exodon
MFK Member
Mar 23, 2017
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I'm in the process of building a greenhouse (unheated) and I plan to put a ~100 gallon stock tank in it to help moderate the greenhouse temperatures (thermal mass). I hope and think that it will not freeze (or maybe just freeze over the top) but I don't know that. Also, even with vents open, in the summer, it will probably get pretty warm.

I'd prefer to not use a bubbler but I'm a little concerned about water stratification and O2 levels. Also, I was hoping a few plants and the sides would be enough surface area for bacteria (nitrogen cycle). However, given those concerns, I may put in a small sponge filter.

Thoughts on a few fish to add? Given the temperature issues, I thought a few North American natives might work.

I've also thought about having a small container (10-20 gallons) for brine shrimp (in the greenhouse). I've read about several people growing them in kiddie pools through the summer. They might last even longer in a greenhouse. Thoughts?

(I live in southwest Virginia, in the Appalachian mountains. Temperatures occasionally get to 0 F, but rarely, and our usual cold spells are in the 20s)
 

Pumpkinseed

Exodon
MFK Member
Nov 6, 2013
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Pennsylvania
You only have a month or two to worry about cold water. You can raise the salinity a touch during that stretch if freezing is a worry. Salt also has the benefit of keeping a number of pathogens in check. A cup and a half of salt in 100 gallons should raise you to about .1% salinity.

I think your bigger problem will be the heat in the summer. I tried to keep a 75 gallon in my garage one year, and it just got too hot for the fish in July and August.

For fish I'm guessing you are looking for something easy since they seem like somewhat of an afterthought in your project. The easiest route would probably be goldfish. Bullhead would be my vote for easiest native.

Fish and plants together just begs for aquaponics, I would highly recommend you research it. Basically you pump your fish water to the plants, which feed on the fish waste, and the plants then clean the water for the fish.
 

Deadliestviper7

The Necromancer
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Aug 6, 2016
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How about orange spotted sunfish and mud minnows?
U can also try hooking heaters and pumps to solar panels.
What's going to grow in the greenhouse?
 

skjl47

Potamotrygon
MFK Member
May 16, 2011
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Hello; You must live somewhat close to me. I live where KY, VA and TN meet on a map. One thing you might need to consider is mosquitoes. They will find the tank during warm weather. Likely not practical to use a screen cover.
Might try some sort of cold tolerant species to keep the skeeters down. Back in the late 1950's I use to catch a small livebearer out of Yellow Creek in Middlesboro KY. They reminded me of guppies and are native to the area. I recall we called them gambusia (sp) but do not know if that name is correct. Better check the rules about collecting natives first.

Gold fish should work but have there own issues. Not sure but maybe white cloud mountain minnows will tolerate the cold??

Good luck
 

Deadliestviper7

The Necromancer
MFK Member
Aug 6, 2016
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Hello; You must live somewhat close to me. I live where KY, VA and TN meet on a map. One thing you might need to consider is mosquitoes. They will find the tank during warm weather. Likely not practical to use a screen cover.
Might try some sort of cold tolerant species to keep the skeeters down. Back in the late 1950's I use to catch a small livebearer out of Yellow Creek in Middlesboro KY. They reminded me of guppies and are native to the area. I recall we called them gambusia (sp) but do not know if that name is correct. Better check the rules about collecting natives first.

Gold fish should work but have there own issues. Not sure but maybe white cloud mountain minnows will tolerate the cold??

Good luck
Gambusia are mosquitofish,
White clouds apparently don't tolerate water below freezing.
A bunch of small fish generally prevents mosquito larvae survival.
 

elting44

Plecostomus
MFK Member
Oct 8, 2007
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Salina, KS
How about orange spotted sunfish and mud minnows?
U can also try hooking heaters and pumps to solar panels.
What's going to grow in the greenhouse?
I think Orangespotted are pretty sensitive to water quality. I think bullheads would do fine. There is a pond in a pasture in my area, one summer it got so dry that the only "water" left in the pond was the consistency of gravy. Only fish to survive were bullheads.

I also 2nd the aquaponics idea
 
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Duckman77

Piranha
MFK Member
May 9, 2005
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Aurora, IL
You only have a month or two to worry about cold water. You can raise the salinity a touch during that stretch if freezing is a worry. Salt also has the benefit of keeping a number of pathogens in check. A cup and a half of salt in 100 gallons should raise you to about .1% salinity.

I think your bigger problem will be the heat in the summer. I tried to keep a 75 gallon in my garage one year, and it just got too hot for the fish in July and August.

For fish I'm guessing you are looking for something easy since they seem like somewhat of an afterthought in your project. The easiest route would probably be goldfish. Bullhead would be my vote for easiest native.

Fish and plants together just begs for aquaponics, I would highly recommend you research it. Basically you pump your fish water to the plants, which feed on the fish waste, and the plants then clean the water for the fish.

Great post! I'm currently looking into starting an aquaponics system with my high school students.
 
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TwoHedWlf

Redtail Catfish
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Mar 2, 2017
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I'd probably go with 1-2 goldfish. Cheap, easily available, leave anything more for after you've had the tank running for a year, see what kind of temperatures it reaches, etc.
 
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