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Stocking levels

Dr. White

Dr. White

Member
Joined
26 Jul 2023
Messages
73
Location
Swindon
I am thinking of adding some gold tetras to my aquarium, but am concerned that it might make the tank too heavily stocked which may result in algae problems, which the tank has been impressively free from since set up in August last year.

I have a 40cm cube (60L), but with an Oase Biomaster 250, this probably adds another 10L or so to the system. Ammonia, nitrates and nitrites have been undetectable since it was cycled. It is heavily planted, but with slow growing species, which have lower light requirements. It is lit by a Kessil A80. Present stock is:

20 cardinal tetra
3 ottos
5 amano shrimp
4 cherry shrimp

I would not want to add any fewer than ten gold tetras. I have been toying with biting the bullet for couple of weeks now, but sort of chicken out a bit. I know they'll have plenty of room and be happy, but am I right to be concerned with the levels? I am sure the filtration is enough to cope with the new stock, and I'd want to watch the nitrates closely. I just don't want to upset the balance, but I also love gold tetras and think they'd make a nice contrast with the cardinals.
 
Dr. White said:
I have a 40cm cube (60L), but with an Oase Biomaster 250, this probably adds another 10L or so to the system. Ammonia, nitrates and nitrites have been undetectable since it was cycled.
Click to expand...

Biomaster 250 in fact adds a little under half that amount of water volume, whilst this helps for water stability, it's doesn't give the fish any actual additional volume to swim in, which in a 40cm cube is limited. I wouldn't have thought 20 cardinal tetra's in a 40cm long cube is ideal to begin with, so I would strongly advise against adding another 10+ fish, regardless if how it may or may not affect the water parameters. I have never kept gold tetra's, I'm sure someone on here has though and can give advice on keeping them.
 
Dr. White said:
I would not want to add any fewer than ten gold tetras. I have been toying with biting the bullet for couple of weeks now, but sort of chicken out a bit. I know they'll have plenty of room and be happy, but am I right to be concerned with the levels? I am sure the filtration is enough to cope with the new stock, and I'd want to watch the nitrates closely. I just don't want to upset the balance, but I also love gold tetras and think they'd make a nice contrast with the cardinals.
Click to expand...
Hi @Dr. White,

My view on your question.
  • On the fish front, assuming 33 adult fish (20 x Cardinal Tetra, 10 x Gold Tetra and 3 x Otto), you would have approximately the same number of fish and fish inches as I do in my 100L aquarium - in fact, you probably will have a little more when I think about the Ottos as well. But I have around 67% more space to deal with that loading. I feel my loading looks quite busy in 100L tank, so that is something to bear in mind when you consider adding more stock. That being said, I personally do not have a problem with overstocking like some others do and have found some benefits - providing your filtration is very mature and aeration is excellent.
  • On the filter front, the Oase 250 would be at 95% capacity to maintain clear and healthy water—assuming you are using the stock sponge and HEL-X13 media. So, the filter aspect itself (as you say) would be enough, but you are pushing the limits of that filter's capability (excluding what you get from your plants).
If it was me, I would say that the stocking and filtration are really on the edge. So when you look at both, you could take the view that it's 'technically' possible, but it's really at the extreme end of the loading capability.

Thanks,
Brad
 
Dr. White said:
I know they'll have plenty of room and be happy
Click to expand...
Really, I'm not so sure?
You could end up with a lot of snippy, stressed little fish, each guarding their own tiny piece of water.
Their size & shape suggest they like swimming, not just pottering about amongst the plants & they won't get that in a 40cm cube. A longer tank would be much more suitable & the fish would behave more naturally.
 
bazz said:
Personally I wouldn't, Gold tetras are capable of growing over 2" (5.5cm) and as such would at least require a tank of 60cm length, longer would be better.

Hemigrammus rodwayi (Golden Tetra) — Seriously Fish

www.seriouslyfish.com www.seriouslyfish.com
Click to expand...
I think they've got that wrong, and I've seen that figure repeated in a some places and different much smaller figures in others. I am more inclined to believe the smaller figures as I kept a couple in a very mixed 4ft tank many years ago. I had them for near on ten years and they never got bigger than about an inch.
 
I have also read they are typically around an inch but can grow to two inches. (For reference, my calculations above are based on the potential full adulthood size of the species).
 
I have never seen healthy, adult size gold tetras only top out at 1 inch...

I understand the temptation to add more fish but I would advise against it just based on the already limited space that you are working with
 
I wouldn’t get them, it’s not even a standard sized 60l but a 60l cube so you have even less space for the fish. Cardinals can get pretty large and some of my older ones are pushing the 2inch mark.

Gold tetras are far more active than cardinals, I wouldn’t put them in anything less than a 60cm long tank. Gold tetras are also not one species of fish but multiple species of similar characins which are affected by a parasite which turns their skin to turn gold, so I’m sure there can be some variation in size too.
 
Eurgh, I’ve kept them mine (Altum unintentional snacks). Sources online are not reliable anymore, they’re regurgitated from single sources. I’ve seen them at about~4.5cm (probabaly more 4), so I bet they could hit 5cm. Check out fishbase for fairly accurate sizing.

Imo, your tank is too small (length) for what you already have, so adding more isn’t ideal.
 
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