Knowing when to stop

jowhiteley

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How do you determine whether or not a tank is overstocked? Is there any way of determining this scientifically eg rate of nitrate production?

If I use more filtration/heavier water changes, can I have more fish?

I'm trying hard to resist the urge to cram too many fish into one tank but it's difficult when there are so many gorgeous fish that I would love to have so I'm just trying to find a way of drawing a line in the sand.
 

bolivianbaby

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I use a few different methods.

1. I watch my fish. Does everyone have plenty of swimming space? Are there any conflicts, etc? Where does everyone swim? Is there still empty space? Do all of my current fish have enough territory?

2. My nitrate levels. If I'm doing 50% weekly water changes on a tank because of 20 nitrates weekly, I'm not going to add more fish to the tank.

Hope this helps!
 

Lucy

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Many people use the 1" per gallon guideline to get started, but other important factors must be considered.
Waste production, swim space, school sizes and territorial issues come to mind.

More filtration and frquent water changes will help keep the nitrates down but will do nothing for swim space and territories.
 

Shawnie

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I agree with BB 100%!
I think swim space and territories is a HUGE one and remembering their needs as ADULTS not what they are now....stunting fish (in the hopes that we will get bigger tanks as they grow) or "my fish will only grow the size of the tank" are major issues for me.....
 

Craig-D

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Obviously, looking in the tank to see if there's enough physical space is key. The fish not only need adequate swim space, but there needs to be places from them to go to get away from the others at times. I define adequate swim space as having a tank that has a horizontal width at least 10 times the fish's length. This means if your fish top out at 2", you want at least a 20" wide tank.

Scientifically speaking, it's my opinion that your nitrate levels will tell you whether you are at your stocking limit. If you perform 30% water changes weekly and yet still struggle to keep your nitrates at 20 ppm or less, you are fully stocked. For example, I perform 20% weekly water changes and my nitrates barely go above 5 ppm, so in terms of water parameters, my system can easily handle more fish.

Looking at your info, you have 21 fish in a 30 gallon tank and most of your fish will grow to be about 2 inches or more. I'd say you are fully stocked, and perhaps will be even a bit overstocked when all those guys are fully grown. A stronger filter and more water changes will help with the bioload, but there is only so much physical real estate to go around and you are at your limit, if not over it, in my opnion.
 
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Prince Powder

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I think swim space and territory requirements are the best route to determining the stock levels. Relying strictly on nitrate levels isn't always 100% trustworthy. You can overstock your tank and still manage to keep nitrate levels lowered by simply having the tank heavily planted. The plants will consume some of the nitrate thereby helping to keep the nitrate levels in check, but your tank could still be overcrowded in regards to territorial aggression and swim space. Food requirements need to also be taken into account. You can have, for example, two small plecos that can easily share a space in regards to swimming and aggression, but will that space allow for enough surface area to grow sufficient algae to keep them both properly fed? If not, then your tank would be overstocked for that area of the tank.
 
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Jaysee

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A large part of it is what kind of fish you are putting in the tank. It's one thing to overstock a tank with tetras....quite another with NW cichlids.
 
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jowhiteley

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@Craig-D Yes, you're right. I made a lot of rookie stocking mistakes and I will be overcrowded once they all grow up. I've got a second tank on its way to correct this.
 
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