Mbuna - When is overstocked too overstocked?

[Nick Park]

I know that overstocking a Malawi tank can help diffuse aggression, but at what point does it become too overstocked? How can you tell?

I've got a 450 litre bow front, and at the moment it's working just fine. There's plenty of rocks, caves and hiding places, and no serious aggression whatsoever - just the usual chasing & jostling that seems to be normal behaviour for mbuna. Water testing is fine apart from fairly high nitrates - but that's unavoidable since the water comes out of the tap where I live at 40 ppm. Lots of filtration (an FX5 and a big Eheim), plenty of oxygenation & regular water changes and filter cleaning.

At present the tank contains three 6-inch synos, a baby syno, a random severum that came with the tank (refuses to die and likes to hang out in a cave with the catfish), four 6-inch acei, two 5-inch honngi redtops, a 4-inch rusty, and about 50 yellow mutt mbuna with some yellow lab in them to one degree or another. Only 2 of these yellow mbuna are fully grown (both female) and they are like baby-producing machines. Most of the fry get eaten, but two or three from each batch manage to hide in holes in the rocks and make it to viability. So most of the fish in the tank are still juveniles, and were born in the tank.

I've seen plenty of photos of African tanks that look more crowded than mine (although usually with much less rock work) and there are no problems at present. In fact the tank has a real wow factor with visitors to our home (I have never seen the point of hiding tanks in a basement, so all my tanks are in the living room or hallway). But I'm guessing that when these juveniles reach full size then I'll be getting near the limits of my tank - even without more breeding. I hate culling fish, but I know my LFS would take some off my hands for their 'Mixed African' tank.

So my question is, how do you know when overstocked is too much overstocked? Is it when fish start dying? Will they naturally stop breeding when conditions are no longer optimum - or do they keep breeding like rats regardless? I've only been in the hobby for a couple of years, so any suggestions are welcome from more experienced fish keepers!

 

[punman]

I have kept 20 adult tropheus (I know, different lake) in a 90 U.S. gallon (340 litre) tank with no issues; keeping up on water changes and very few rocks in the tank. I would not want to put much more than that in there. If your tank is one-third rocks then you only have 300 litres of water, about the same as my 90 gallon with my few rocks.

How do you know when overstocked is too much overstocked? That is an interesting question depending upon many variables but I will say this; there is a difference between fish surviving and thriving. Just because fish are not dying and still reproducing does not necessarily mean they are thriving.

 

[Nick Park]

 

[Christophercanary]

That is a beautiful tank and somewhat exactly what I'm going for! I've kept SA/CA Cichlilds for 15 years and I just bought my first African cichlids the other day! Thanks for sharing this photo, I was reading your posts hoping that you would show a picture. You weren't kidding about the wow factor.

Now I've never kept african communities so I can't exactly answer your question but I've kept many sa cichlid communities and in my experience as long as fish aren't getting bullied into isolation/losing fins, scales, etc. then you may be able to get away with the overcrowding. I personally don't like overcrowding sa cichlids because most of them just get too big and could use the less crowding and tank space.

I think just watching and observing your tank enough you will know when the rappore in the tank is to your comfort level and then you can adjust from there however your tank in that picture appears to have just the perfect amount. I personally wouldn't do more fish than that and if they breed I would get rid of some fish to match the number you have in that picture.

Anyway, thanks again for sharing.
C.

 

[neutrino]

Mbuna and most other Malawi cichlids are determined breeders, undeterred by tank size, imperfect water quality, being crowded, even no mates of the same species. Imo you're just fine for now. Later on you may need to catch out and bring a few to your lfs now and then, depending how many fry survive to grow up.

 

[duanes]

As long as aggression is minimal, it's not about fish numbers, it's really about water quality.
If your filters and water changes are able to handle your nutrient load goal (stable pH, low nitrate, 0 ammonia and nitrite), you are all good.
But if you can't keep nitrate down with the amount of water changes you do, or your pH dips too much between water changes, then maybe your tank is either overstocked, or you need to up your water change amounts, and schedule for the amount the tank is stocked with.

 

[DJRansome]

I like to stock by length (not gallons) so 20 mbuna in a 48" x 18" tank for example. Measure on the side for depth...not the middle when measuring a bowfront.

I also want the fish to have room to show some of their natural behavior and have room to move for reasons other than dodging his neighbors.

 

[Longmayitreign]

Short answer: It looks fine.