Should I add an algae-eater to this tank?
I currently have 47 three-month-old kribensis growing on in a fry tank. I’d like to add a plant-friendly clean-up crew, if possible, to get rid of any leftover food as well as the algae that’s started growing on the rocks and glass. Please could you advise?
NEALE REPLIES:
There are no fish or shrimps that clean up algae sufficiently well to be purchased for that reason alone. Yes, there are some fish that will eat algae, but these are usually rather picky about what algae they eat.
Ancistrus and Otocinclus will certainly eat green algae and diatoms, but largely ignore so-called red algae, such as brush, beard, and hair algae and won’t touch blue-green algae—also known as cyanobacteria—at all. These are consumed by very few fish species, and almost always have to be controlled in other ways.
A few fish species will eat red algae, but often solve one problem and cause another. Take the ever-popular Siamese algae-eater. While a fine fish in many ways, it’s fairly big when fully grown at up to 15cm long, and comes from moderately fast-flowing habitats, so needs a decent current and plenty of oxygen. Singletons sometimes become bullies, or at least annoying to other fish, though in small groups of 5-6 specimens this species usually settles down and behaves very well. So, while it’s a perfectly useful algae-eating fish in a large, well-maintained aquarium, it’s not an ideal choice for a small tank.
Really thick growths of red algae might be beyond the abilities of even Siamese algae-eaters to handle, and if anything, they’re more about inhibiting re-growth than actually ‘mowing the lawn’ down to nothingness. I have seen
Ameca splendens devour long threads of hair algae, but the downside here is that these lively and colourful herbivores are also rather feisty—even nippy at times. They’re fabulous for a species tank or a carefully set up biotope, but not really community fish.
Adding fish—algae eaters or otherwise—increases the rate at which nitrate and phosphate accumulate in the water. This, in turn, increases the rate at which algae can grow.
The best way to handle algae is to either ignore it if you can or else maintain the tank in such a way that algae can’t thrive, either by more water changes to lower nitrate and phosphate levels or by adding fast-growing plants such as Hygrophila or Vallisneria that will keep algae types in check by outcompeting them for nutrients.
Mind you, your fish might not care about algae. Blue-green algae can indicate suboptimal conditions, for sure, but the other types are pretty benign. Additional water changes might be necessary to lower nitrate and phosphate levels—and it’s worth noting that cichlids are more sensitive to nitrate than most community fish, so aim to keep levels below 20 mg/l if you can. Above that, cichlids seem to become stressed and disease-prone, some species more than others, but dwarf cichlids of all sorts tend to be towards the more sensitive end of the range.