Algae control for my goldfish/koi tank

Are there any "cold" water algae eaters I can get for this tank?
I need something big enough that the koi won't eat them.
I used to have Oto cats, til I found the koi eating one.

So, what are your thoughts?
This tank has a sand bottom.

What is the current temperature of the koi tank? Is it room temperature? And how big is the tank?

I am not an expert on plecos; but I'd like to say the common pleco could survive; however, it totally depends on the currrent temperature on tank and size.

Plecos are more warm water than cold water. I had one in my 130 gallon ID shark tank.
The goldfish/koi tank is around room temp and is 125 gallon.

I would avoid the plecos, as they are warm water fish and the koi/goldfish are cold (as mentioned above). As you have seen the otos turn into food, and would be quite stressed in a cold water tank too.

There is not much I would suggest for "creatures" to feed on the algae in a cold water tank. Even in a tropical tank (which there are some options), my main suggestion with algae is to look for its root cause, rather than treating the symptom.

1. Look at decreasing lighting, especially in duration, but also in intensity. Another thing to consider if the tank is on a timer, is having broken periods of light (for an hour or two on, then off). It has been suggested by some that some algae growth can be inhibited this way.

2. Look at the nutrients and waste in the water. Decreasing feeding amounts and frequency can reduce some algae. Larger and more frequent water changes can also help.

3. Physically remove the algae

The only lighting either tank has is when I happen to have the living room light on. The goldfish/koi tank is in the dining room next to a window with the blinds closed. The dining room light is rarely ever turned on.
I do #3 when I notice the splotches.
There seems to be algae eating shrimps, but since the algae is on the glass, don't think that would work.

Sandman1969 wrote:The only lighting either tank has is when I happen to have the living room light on. The goldfish/koi tank is in the dining room next to a window with the blinds closed. The dining room light is rarely ever turned on.
I do #3 when I notice the splotches.
There seems to be algae eating shrimps, but since the algae is on the glass, don't think that would work.

Amano shrimp are great algae eating creatures in well planted tropical settings, but not in a cold water tank. Plus if the otos were snacks, the amanos would last even less.

Could you snap a couple shots of the algae? There are so many varieties, and identifying the type can help us give you better suggestions. Sometimes water current can also play a factor. Some types of algae even seem to flourish in lower light settings.

So no natural light on the tank whatsoever?

I'll see if I can when I get back home. But it's brown algae. Shows up in different areas of the tank.

I have Ancistrus in a couple of tanks, but way warmer than what a koi or goldfish would be in. To me, the one and only reliable algae cleaner is the fishkeeper with a painter's razor blade. I get brown algae (diatoms, actually) in my house plumbing. It appear in the tanks fed by my municipal water if the:
a) tanks are overcrowded;
b) the fluorescents are too old;
c) the light is dim.

99% of the time, I have to get scraping in overstocked grow out tanks - rarely in planted, lightly stocked aquaria. It comes back around to the usual - keeping goldfish and especially koi indoors in aquariums is a load of work. Too much work for me - the last time I cared for goldfish and koi over a winter at the school, I think I spent more time on the 3 tanks they were in than I did on my entire fishroom at home.

So my answer would be that there are no algae eaters you can use in that tank. You have to scrape it down with every big water change...

Scrape it off and filter it out is probably all you can do. My tanks are not meant to be overly appealing so I don't bother, besides they are bare tanks viewed from above. Algae is a primitive plant form and it grows when conditions are ideal for it's growth. Which usually means to much waste in the water. Dialing back on the light and food can help and more frequent water changes.

A pleco will only add to the problem in my opinion. If they do survive at that water temperature they will only increase the waste in the water as that algae comes out the other end.

Steve

I just remembered....how about pond snails? I know a friend who brings his kois indoors with few pond snails during cold season time and they have survived in room temperatures. He is consistent with his water changes and over filters the tank. Hope that helps..

The koi ate the snails in my school tanks. Plus the pond snails were useless against algae.

I have seen released plecos in 10 degree water in Florida, but plecos are lousy algae eaters that poop like horses.

The temp is roughly 25 degrees cel. There's just one koi & one comet goldfish. Lighting is just ambient lighting, no lights specific to either tank.
I do clean the algae off using a magic eraser. Works well.

A good start is to get the temps down to healthier levels. That is the mid summer danger zone for fish like that. At this time of year, they should be as cool as you can manage.

This will slow down their metabolisms and reduce the amount of food you need to pour in. Less food for the algae. Cooler water means more oxygen for the fish, too.

Other than putting a bunch of frozen water bottles in the tank 24/7, there's no way to bring it down.

Strange thing, my 130 gallon ID shark tank, is heated, in the same room but opposite side of and no algae issues at all. It's temp is 78 F currently. No algae control and yet no build up at all.

The ID shark isn't a herbivore like the carp. The algae may be feeding on the different location's light, but the poop from the goldie and koi are its nutrition. Carp have really inefficient digestive systems, and their wastes are still full of good algae food.

That's a hot room! At this time of year, my house sits around 19, and my fishroom at around 21-22.

That temp was taken from one of those stick-on thermometers.
The digital thermometer I have states it's around 75F. My apartment is around 62F.
No clue why that tank is almost as warm as the heated tank. While there is a heater in it, I never see it turn on.

I'd suggest you unplug and remove the heater.

Stick on thermometers don't say much, and the digital is probably closer to real reading. It would seem to me that heater is working fine, and shouldn't be. Remember that as the temperature falls to the cooler goldfish/koi range, you will have to adjust feeding to their slower metabolism.

I did unplug it the other day. No change.
The temp on the sticker, with a 2 degree dif from the digital, is still around the 25 C mark. There is no heat source turned on in here.

Hmm. Could you have a filter motor running hot? That much above room temperature would make me check everything there. Sun could heat a tank, but it would fluctuate.

I just checked both HoBs, very very very slight bit of warmth to their motors.
I have the canister, but cannot tell if it is by touch.

The window that is at one end of that tank has a blind but it's always closed. never any direct sun.

I would get a 3rd thermometer and check. if your house is at 16 and your tank at 23 unheated - that defies logic. You have a cold house and a warm tank sitting in it. Something doesn't add up - if you were running a heater it would burn out fairly quickly trying to bridge a wide gap like that.

I have one of those glass floating thermometers in that tank as well. The mercury is just barely above the green mark, if that helps. Can't read what it actually is, but think it's just above 60.

Logically, the tank with no heater will be room temperature. Get rid of the wonky thermometers, and pick up a working one somewhere along the way. But if the heater is unplugged and removed so the koi doesn't bash it around and break it, you know the temperature in an unheated tank out of direct, blazing sunlight.

The digital one I use for the ID shark tank is one that someone here suggested that they use and bought from ebay. There's a 2 degree difference between it & the sticky ones.
So the glass ones are wonky too?

It's not a type that's bad, but individual thermometers. When I used to buy the steel and glass hang on ones, looking at them in the store would show many different temperatures on the same rack. Usually, half a dozen in 10 would show consistency, so I would pick from them.

I now use a temperature sensor I point at the tank and get a reading from. One is good for all my tanks, and it is accurate enough. It's probably not perfect, but it is unlikely to be more than a degree off. I double check it against some high quality temperature sensor digitals I use, and it gives the same readings.

The key is to double check. If the tank is unheated, knowing the room temperature should say a lot. Today, my fishroom is at 22. The top rack tanks are at 22.5, mid level 21 and lower rack at 19. Once the heating comes on in there is a few weeks, I'll run a small fan to even temps out. I pick my fish by the temps I can offer without heating more than a few tanks. It'll overwinter at an average of 22.

Right now, the room is heated by the water heater in the corner and the seasonal daytime temps and decent room insulation keep it from dropping much.