Will Plecos Eat Fry?

MagicSmokeAquarist

MagicSmokeAquarist

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Nov 14, 2020
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So I'm currently breeding fancy guppies, and soon some fancy goldfish, but I have had a recent algae problem. I put in some algaecide, but I still have pre-existing algae in there. To help prevent algae, I decided to get a cleaning crew (obviously). So I was going to buy some cherry shrimp. Too big to be eaten by the guppies, but not so big, or fast that they would eat the fry...until I read on my algaecide bottle that it kills crustaceans, including shrimp.

So, instead I started researching plecos. I've never kept one, personally, but I know some strands (like the common pleco) get big. I wanted to keep them small, as my guppy tank is only 29 gallons. I eventually found the bristlenose pleco. It only gets 5 inches, and apparently is a great algae eater.

I have a few questions:

  1. Will this specific pleco try to eat the adult guppies and or the fry?
  2. Are they at all peaceful?
  3. I have quite a bit of algae, and I understand it might need more food. Will it eat my semi-floating pellets I put in there everyday? (do note it's as small as a ball-point on a pen)
  4. Will they eat algae off of rugged rock, and off of leaves?
My primary concern is that it will try to eat the fry. Any fry I may have.

Any info is greatly appreciated!
 
If it finds eggs on surfaces it may eat those, but most healthy fry will stay out of its way. It may take a few if weak, sick, or dead though.

But keep in mind they don't eat all kinds of algae, only soft algaes. Usually algae comes from too much light or too much or too little nutrients, etc, so finding out why you are getting algae will be the first step to getting rid of it.
 
Noodlecats is exactly right algae is caused by an imbalance. The best algae eaters are fast growing live plants. Just provide the right conditions and they will outcompete algae. Yes you will need to prune the plants but no pet (in this case the tank) is without maintenance. It is a myth that you need an algae eater in the aquarium. I wrote an article on this site, I thought it was a sticky but I can't find anymore. In short there are many different types of algae and algae eaters only eat a couple of those at most. But they still produce waste, which is nutrients for more algae (but probably not the kind they eat). So an algae eater could actually add to your problem. Only keep algae eating fish if you think they are interesting.
 
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Yeah, I know that you can't solely rely on algae eaters. I was not familiar with the plants to prevent algae, however. I know they keep your water balanced, but not prevent algae. I've never been good with plants. I have a layer of nutrient substrate, and on top, sand. I have very, very beginner plants, and some of them (within a few weeks) are already dead in that tank. I even have a full spectrum light.

The only thing I can think of that is going wrong in that tank with the plants, is that I only have 3 baby guppies in the 29 gallon, so it may not be enough ammonia for the plants to consume and turn into nitrates? When thinking that aloud, I also remember ammonia and nitrites are supposed to be at 0. (both are in my 29 gal)

So, I'm kinda lost. Just checked my tank and EVERYTHING is where it should be in terms of chemicals.
 
Do you have a photo of the tank?
What kinds of plants?

Having TOO LITTLE nutrients can contribute to algae too.

How long are your lights on? Sometimes doing 6 hours of light is good enough for the plants but not enough for algae, sometimes people find it best to cut their light time up into 2 blocks during the day (example 3 hours on, 2 hours off, then 3 hours on again).

I'm all for people getting plecos suitable for their tank size, and BN plecos are phenomenal and fun fish, so by all means if you like them, go for it, but they need foods besides algaes too.

Some of the best plants for algae are floating ones. Hornwort or anacharis floated on the top is good, it shades out the lower ones a bit and is fast absorbing of nutrients plus are low maintenance. Other floating plants like frog bit or water lettuce can be good.

Careful with duckweed because once you have it, it may never leave if it does well for you lol (usually does well, too well).


How long has this tank been set up? New set ups are prone to diatom blooms, basically a soft powdery brown covering everything. This is pretty normal and often goes away with time, but nerite snails love this type of algae I find.

Get a photo of the algae. Certain algaes can be stubborn and difficult (blackbeard, staghorn) to deal with while some are totally easy (diatoms, brown, green dust). But there's also cyanobacteria that's often mistaken as algae which needs a whole different look at (the loach has a good treatment for this one if thats what it is)
 
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Here are some photos.

This is really embarrassing, but we have some family over right now, and a small one got ahold of some of the fish food and tossed it in there. (that's the white dust you see)

Anyhow, the algae, as you can see, is almost like a carpet. I don't know what else much to say, but I hope these images help.
 
Certainly not my best tank, if you ask me. And pretty ugly...I just wish the plants would do well, then maybe it would look nice. I've always preferred a natural look to aquariums, but I was on a budget and I needed to fill some spaces, so I got the dragon and the little japanese lamp thing lol
 
Oof thats some bad algae. I almost want to say blackbeard

Honestly, the scape itself looks like it can have some good potential once it fills in, but that algae is pretty bad lol

I would opt to split your light time into 2 small blocks of on time combined with some anacharis or hornwort floated up top (plus guppy youngsters love this).
So do 3 hours on, then 2 hours off, then 3 hours on again. Gives plants enough light but interrupts algae growth.

Perhaps some of the hardscape that can be removed, take it out and give it a small Scrub with hydrogen peroxide, then a very very good rinse before going back into the tank. Just to give the tank a bit of a boost in getting back into shape
 
Yep! They'd really help with excess nutrients in the water.

Also, don't feel bad about how it looks, you're here asking for help, so how it looks will matter most when you get it back in good shape ;)
 
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