# Why are my ember tetras so shy?



## Elliott_Fordham (13 Apr 2020)

Hi all, 

This is my first post on the forum and I'm starting off with some trouble.

The ember tetras I have in my aquarium are really shy and hide all day until I feed the tank. It is heavily planted with lots of light and a filter with a decent flow. My shrimp seem to be active and so do the snails. My fish just don't swim around like they used to  Does anyone know where I may be going wrong?

Thanks and I have listed tank specs below.

*Maintenance
*
50% Tap water change once a week


*Equipment*
Aquarium = 30x30x30cm Evolution Aqua Aquascaper with glass lid. 
Light = Twinstar 300E light - 15 Watts
Filter = 270L/hr corner with spray bar
Heater = Aquael 25 Watt heater. 
CO2 = No 
Planting = Heavily stocked on plants (foreground, midground and background)
Hardscape = grey mountain stone, manzanita wood

*Parameters*
Temp - 25 degrees C
Nitrate - 25ppm
Nitrite - 0ppm
Ammonia - 0ppm
pH - 6.8
KH - 6 degrees
GH - Unknown


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## Tim Harrison (13 Apr 2020)

Welcome Elliot 

It could be that your aquarium is perhaps a little on the small size for Ember Tetras. An aquarium with base dimensions of at least 45 ∗ 30 cm or equivalent is suggested. It could also be that the light is too bright, the filter output too strong.

Take a look at what Seriously Fish has to say about Ember Tetras. You may get to the bottom of it yourself. But, if you can post a pic or two of your tank it might help others diagnose what is wrong too.


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## dw1305 (13 Apr 2020)

Hi all,





Tim Harrison said:


> the filter output too strong


You could try turning the filter off when the light is on and see what happens.

I'm a <"floating plant fan"> for small <"timid fish">, it just makes them feel more secure.

cheers Darrel


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## sparkyweasel (13 Apr 2020)

They like a dark substrate, or one covered in leaves etc.
They also thrive best in large groups, but on the other hand, you don't want to overstock. How many have you got? Any other fish?


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## Elliott_Fordham (14 Apr 2020)

Yes maybe it is a bit small which may be causing issues. I will attempt to lower the filter output but unfortunately I can not dim the light. Floating plants maybe a good idea, would they block out a lot of light from my submerged plants? I think the most demanding plant I have is mincrantheum monte carlo. I currently have 7 in a group with 3 cardinals tetras and 2 pygmy corydoras. what floating plants would you recommend? 

Thanks everyone!


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## dw1305 (14 Apr 2020)

Hi all,





Elliott_Fordham said:


> Floating plants maybe a good idea, would they block out a lot of light from my submerged plants?.....what floating plants would you recommend?


They do, but you can adjust the number to give you enough light at substrate level. If I have a really bright light I just have a thick layerer of floating plants. My "go to" floating plants are Amazon Frogbit (<"_Limnobium laevigatum">_) as a surface floater and Hornwort (<"_Ceratophyllum demersum">_) as a sub-surface floater, but <"there are other options">.

I use the health and colour of a floating plant (so not CO2 or light limited) to give me a <"visual indication of nutrient status">. I called this the <"Duckweed Index">, and _Limnobium_ is a nice leaf green colour.





Elliott_Fordham said:


> currently have 7 in a group with 3 cardinals tetras and 2 pygmy corydoras.


OK so you can't add any more fish.

Do you feed any live food? I haven't kept Ember Tetras, but Pygmy Corydoras <"really like micro-worms">, and I'd be surprised if the Ember Tetras didn't also like them. Because they are a really small food item, it takes the fish a long time to hoover them all up and that might get them out and about a bit more.

cheers Darrel


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## Dr Mike Oxgreen (14 Apr 2020)

Elliott_Fordham said:


> I currently have 7 in a group with 3 cardinals tetras and 2 pygmy corydoras.





dw1305 said:


> OK so you can't add any more fish.



I’m not so sure it’s as clear-cut as that. This is always going to be a blurry area with different rules of thumb, some more conservative than others, but one such rule that works for small fish is “one centimetre of fish (excluding tail) per litre”. I reckon he’s got about 20cm of fish at the moment, more or less, and that’s in a 27 litre tank (nominally). So in my opinion, with good tank husbandry he could perhaps add 2 or 3 more embers, and this might make the difference to their confidence.

Actually, I would find an alternative home for the cardinals (despite me being a big fan of them). They won’t be especially happy in just a threesome, and being slightly bigger than embers they are probably taking the capacity of roughly four embers.

That said, you do have to consider the fact that a cube-shaped tank has the minimum footprint, so I’d probably not go right up to 27cm of fish. But without the cardinals there is definitely room for 3 or 4 more embers to go with the 7 he’s got without pushing the limit. I also think small tanks look better with just one shoaling species.

I also keep a similar size tank, albeit rectangular. Coincidentally I also have embers and Pygmy cories. There are periods when none of my embers are visible - they are all hiding deep in the undergrowth. But then, five minutes later many of them will be out and about. I just think it might be normal behaviour, and the fish simply make use of the fact that the tank has plenty of hiding places and choose to take an occasional “fag break”. You see pictures of some tanks with virtually no hiding places, and the small fish are out in the open because they have no choice.

I also have Amazon frogbit, which I confine to each end of the (rectangular) tank using threads of polyester tied to suction cups. I have been gradually reducing it because in a small tank its roots interfere with the “picture” of the tank, and the embers often strut about in the bright area in between the rafts of frogbit. So I do think small fish can be acclimatised to less cover, although it helps to start with lots of cover first. Frogbit or hornwort are great for this. I doubt hornwort would survive a postal journey, but I bought my frogbit from eBay and I’m very pleased with it.


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## sparkyweasel (14 Apr 2020)

Dr Mike Oxgreen said:


> Actually, I would find an alternative home for the cardinals (despite me being a big fan of them). They won’t be especially happy in just a threesome, and being slightly bigger than embers they are probably taking the capacity of roughly four embers.
> 
> That said, you do have to consider the fact that a cube-shaped tank has the minimum footprint, so I’d probably not go right up to 27cm of fish. But without the cardinals there is definitely room for 3 or 4 more embers to go with the 7 he’s got without pushing the limit. I also think small tanks look better with just one shoaling species.



That sounds like a good plan.


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## Elliott_Fordham (14 Apr 2020)

Thank you for the suggestions on the floating plants will definitely try some out! Frogbit on ebay looks like a good shout. The cardinals were left over from a tank disaster I had where I lost the majority (heater sticking on) and only have one aquarium. I could give them to my LFS potentially for a discount on some more embers. I tried reducing the flow today and had no luck unfortunately. I think they were even less inclined to come out. 

Thanks for the advice everyone


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## Elliott_Fordham (17 Apr 2020)

Hi All 

Just an update - My filter is really quiet so I have never noticed this before but as I was doing some maintenance today I realised that my filter quite heavily vibrates my tank. It's a corner filter and cost about £10 so nothing expensive. Could this vibration be causing my fish trouble? Let me know what you think and also if you know of any discrete internal filters that would not vibrate as much could you post them in here.As a side note I can't have a canister because I have to have a lid as the room I have the tank in will get damp without one. 

Thanks


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## alto (17 Apr 2020)

Elliott_Fordham said:


> my filter quite heavily vibrates my tank.


most fish are sensitive to vibration so I would explore this 

I often use an Eheim Mini Up filter in my 30C BUT I seldom keep fish in these tanks - and I just touched the glass and can feel the _hummmmmm
_
Can you not just do some cutouts for filter inlet/outlet - obviously this would require some preparation


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## Elliott_Fordham (20 Apr 2020)

Yes I will investigate this as I believe it is a possibility that the vibration is causing the timidness of my tetras. I have a glass lid and to do cut outs would require various pieces of equipment that I don't own  I might however try my cannister with the lid off as it's summer now and the walls of the room are warmer. 

Thanks for the advice


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## alto (20 Apr 2020)

As you’ve the canister filter already, easy to try this - cling film makes a decent temporary lid 

Can you slide the glass forward/sideways a bit to allow room for the canister - use some self stick tabs to keep the glass in place, sorry no idea of the proper name but you can see them in Jurijs mit JS video DOOA 20 x 20 x 20 @3:25


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## dean (25 Apr 2020)

I’d say you group is too small for them to feel secure 
Especially as you have small numbers of two other species that will also feel insecure 

My suggestion would be to go with just one species in a small tank then use shrimp and snails as the clean up crew 


Sent from my iPhone using Tapatalk


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## Elliott_Fordham (30 Apr 2020)

*Update:* I have switched to the canister filter and managed to secure the lid in a slightly different position. It's is helping with algae but fish haven't really changed their behaviour. I think potentially the light is just to bright for the lil guys. Gonna order some floating plants off of Ebay and when I'm able to go to the LFS return the cardinals and but a couple more embers and shrimp. 

Thanks all


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## Dr Mike Oxgreen (30 Apr 2020)

I’m not convinced that the bright light is the issue. I have seen mine all out and playing boisterously in the brightest part of the tank, where only an hour or two earlier they were all tucked away.

In fact, I think I have noticed that they become bolder and more active as the lighting period continues. I am wondering if this is actually an oxygenation issue, so I’ve ordered another electronic timer so I can run an airstone overnight. I don’t think it’s a CO₂ issue, because I’ve seen them at their most active when CO₂ is very high (drop checker very light green).


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## Dr Mike Oxgreen (30 Apr 2020)

I’ve just looked up the spec of your light.

I acknowledge that lumens are not the ideal measure, but as is often the case it’s all we’ve got. Your light is 1,100 lumens, giving about 40 lumens per litre. This puts you on the cusp of high lighting.

But... I’ve got about double that, around 80 lumens per litre, and my tank is shallower. Some might say that’s too much, and they might be right - but as I say I regularly see my embers frolicking about in the brightest part of the tank. But I’m suspecting I only see this towards the end of the photoperiod.

Purely from an algae point of view, I’d say you’ve got too much light, given that you’re not using CO₂ - but I’m not convinced this is the problem from a fish behaviour point of view.

Now in my tank, I am using generous CO₂ and therefore photosynthesis is somewhat turbocharged. Towards the end of my lighting period I get a lot of bubbles on my plants and rising up from them. This indicates that the water has a high oxygen content, but it takes hours to get to that state - maybe four or five hours. Perhaps this indicates that my water is rather low on oxygen at the start of the photoperiod (it is densely planted, and the plants are net consumers of oxygen overnight), and this is why I intend to start experimenting with an airstone overnight.

I just wonder, if I’m right about low oxygen in my tank, maybe that’s your issue as well? Can you reposition your spray bar or lily pipe to give stronger surface agitation, and/or experiment with an airstone?


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## Dr Mike Oxgreen (30 Apr 2020)

Something else you could try regarding oxygen is turning the temperature down a bit. I’ve got my embers at 23°C and they seem perfectly happy at this temperature. Is it worth knocking your temperature down a degree or two to further test the oxygen hypothesis, in addition to increasing surface movement?


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## Dr Mike Oxgreen (30 Apr 2020)

Apologies for a further reply!

As I sit here now, my embers were hiding away at the start of the photoperiod. But now, four and a half hours later, the embers are out and about. The ballsy males are flexing their muscles, and there is some jostling for rank. All normal stuff. They are not schooling tightly, which to me indicates stress in most species. Meanwhile, bubbles of oxygen are rising from the hairgrass and HC Cuba, and starting to accumulate on the _Hottonia palustris_ and _Rotala walichii_. 

So once again, the embers’ activity correlates with oxygen. CO₂ is pretty high, with a lime green drop checker.


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## Dr Mike Oxgreen (2 May 2020)

Well, I set up an air pump and stone yesterday, intending to switch it on before I went to bed - but I forgot!

However, I did switch it on for an hour and a half this morning, before the CO₂ switched on.

And the difference in the embers’ activity level is remarkable. Right from the beginning of the photoperiod they’ve been moderately active, where before I’d expect them to be hiding away until well into the photoperiod. And this is with only 90 minutes of aeration - I’m excited to see what things might be like if I aerate for a longer period.

I’ve now got another electronic timer and have programmed it to power the air pump overnight until the morning.

So it’s early days yet, but it does appear that my heavily planted tank might have been oxygen-depleted overnight. I really wonder whether this might also be @Elliott_Fordham ’s problem as well.

I strongly recommend experimenting along similar lines:  have an air pump come on overnight, switching off before the CO₂ comes on. With luck, @Elliott_Fordham might be pleasantly surprised by the change in the embers’ behaviour!


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## Elliott_Fordham (3 May 2020)

Hi @Dr Mike Oxgreen

That sounds good I will have to try that out! I don't usually run air stones in my scapes for the risk of it looking unnatural however running one at night maybe a huge advantage to my embers behaviour. Do you know of any small and quiet air pumps I could buy as current lockdown means I can't get mine from my other house. 

Cheers 
Elliott


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## Dr Mike Oxgreen (3 May 2020)

I only have one air pump, so can’t really compare its noise level. But I’ll only be running it at night, so I’m not greatly concerned about that aspect of it.

Since this is very much an experiment, I’d simply buy the cheapest small pump you can (with air line, stone and check valve), and if it doesn’t solve the problem simply keep it as a piece of emergency equipment.

I agree about not wanting bubbles in your tank’s picture, but you won’t want the air pump running during the photoperiod at the same time as CO₂, since the bubbles will simply be driving off CO₂.


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## Dr Mike Oxgreen (4 May 2020)

Just a little update on this...

I think it’s now been three days that I’ve been running an air pump - now plugged into a timer coming on at 01:00 (3 hours after lights out) until 09:55 (5 minutes before CO₂ comes on). I figure that after the end of the photoperiod there will be decent oxygen for a few hours before it needs boosting.

And my embers have never been so active! Gone are the periods when none of them were visible; now, there’s a decent number of them on show, centre stage, all the time, jostling, bickering, asserting pecking order, etc. They also seem slightly less quick to scarper when there is movement near the tank.

It has taken me a while to figure this out, because I didn’t believe oxygen could be a problem in a heavily planted tank, and also because I attributed the languid behaviour to excess CO₂ - in fact a few weeks ago I was experimenting with reducing CO₂ to hardly anything. This didn’t improve the embers’ activity, but it has given me a few tufts of BBA to contend with!

I may yet experiment with increasing my CO₂ bubble rate, which will enable me to shorten the “pre-gassing” period prior to lights-on, during which there is no aeration or photosynthesis.


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## Elliott_Fordham (5 May 2020)

Hi @Dr Mike Oxgreen 

Glad to hear you are having a lot of success with your ember tetras! My air pump arrived today and I have plugged it in to run over night, forgot to buy a timer though because I thought i had one. Will get one over the next few days. I hope I have similar success to you, similarly I thought that oxygen wouldn't be an issue in a planted tank but I guess it is. Have you ever used a Twinstar water steriliser, they work by electrolysis and produce oxygen and hydrogen micro bubbles. I would like to try one to see if they help with the oxygen issue but unfortunately don't have the cash to buy one atm as they are quite expensive. If they worked it would be a nice replacement to an airstone. 

Thanks
Elliott


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## Dr Mike Oxgreen (6 May 2020)

Yes, I’ve got a Twinstar M3 in my tank. I notice now that the oxygen bubbles linger in the water for much longer. Previously they dissolved in about 10-15 seconds, but now they hang around for at least 30 seconds. I think this indicates that the water has more oxygen in it than before, but also tends to suggest that the air pump running overnight has a more powerful oxygenating effect than the M3.

I really hope you get the same effect as I have, because the change in the embers’ behaviour has been amazing.

Have you reduced your CO₂ period as well? That might have an effect, but it didn’t for me. However, your CO₂ period was rather too long!


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## Andrew Butler (6 May 2020)

Hey @Elliott_Fordham 


Elliott_Fordham said:


> I can not dim the light.


You have the Twinstar 300E, correct? I'm quite sure this is an easy solution and you can dim it very easily, I can't see anyone else mention it so sorry if they already have.
There's a nice, cheap solution which will control both the time and light intensity; it's sold under various names and brands but look at the picture below for a couple of examples.
I do have a couple spare at the moment which are new and I'm sure I can help you out. 


Elliott_Fordham said:


> I have a glass lid and to do cut outs would require various pieces of equipment that I don't own


You might be surprised on how easily and cheaply this can be done in a fashion if you haven't found 'a proper' solution yet? - I've seen you've found a way but unsure what that is.
_This will depend on the type of glass you have_

Onto the Ember Tetra, I have a larger group than you and up until a few days ago were in a smaller, temporary aquarium around the same volume as yours where they were quite content but they are now in a much larger tank and whereas the Neon Green Rasbora spend most of their time out in the open, the Ember Tetra seem to enjoy the cover. Maybe also worth noting that from time to time the Ember Tetra enjoy coming out and swimming into the much stronger flow. My aquarium display dimensions are based upon those of an AS900, lighting is a Twinstar 900S on around 70%.


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## Ray (6 May 2020)

Interesting.  I may be imagining this but I seem to recall reading that Amano himself recommended raising your filter return at night to provide surface agitation and so better aeration.  So this is certainly a thing.

As an alternative to an airstone, if you still wanted to automate this you could perhaps have a small pump with a spraybar that was above the surface.  I’d be interested if that has the same effect on Ember Tetra behaviour...

Or just run a HOB filter of course, but that’s not very CO2 friendly!

Smarter minds than mine might also be able to conceive some kind of aerator that could be in the filter return run safely hidden inside your cabinet...


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## Dr Mike Oxgreen (7 May 2020)

Just to illustrate how active my embers are now, just with overnight aeration...




(That Pygmy Cory is doing a very poor impersonation of an ember tetra, but he’s putting everything into it!)

And yes, I should clean off the diatoms from the end walls.


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## Elliott_Fordham (8 May 2020)

Hi @Dr Mike Oxgreen 

Those Ember tetras look great! Swimming around loads! I've been trying with the airstone for a couple nights now and haven't really seen much change? is your light slightly dimmed or dimmer specs than mine just out of curiosity?

Thanks 
Elliott


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## Dr Mike Oxgreen (8 May 2020)

I’m putting something like 2,000 lumens into this tank, so it’s very high light. And now the embers don’t seem to care about the bright light. I do have some frogbit, as you can see in the video, but I use polyester thread to constrain it into two sections at the ends of the tank - in the middle there’s no cover at all.

That’s a pity it hasn’t worked for you, because for me the change has been huge. I really hoped I had hit upon the solution to your problem as well as my embers’ occasional reticence.

Maybe, just maybe, the presence of the frogbit at the ends does give the embers the confidence to roam around the uncovered areas. But before my nocturnal aeration they were often hiding despite the frogbit, so maybe they need both the oxygenation and a bit of cover at the sides?


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## Elliott_Fordham (8 May 2020)

Yes i think that is potentially the solution to the problem as the light is off in my aquarium and all the embers are swimming around freely in the open areas. I'm thinking about a ramp up ramp down dimmer to attach to my light to see if that helps things. I've heard they are great for the plants as well. I will update you on my progress when I get the dimmer.

Cheers


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## Ray (12 May 2020)

Andrew Butler said:


> Hey @Elliott_Fordham
> There's a nice, cheap solution which will control both the time and light intensity; it's sold under various names and brands but look at the picture below for a couple of examples.
> I do have a couple spare at the moment which are new and I'm sure I can help you out.



Would that work on a ONF FLAT NANO LED light? That’s 15W, the dumb one with 3 pre-set dimming levels not the smart one with an app.


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## Andrew Butler (12 May 2020)

Ray said:


> Would that work on a ONF FLAT NANO LED light? That’s 15W, the dumb one with 3 pre-set dimming levels not the smart one with an app.


My honest answer is I'm unsure.  I cannot remember the wording but it's something along the lines of continual/constant power.


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## hypnogogia (28 May 2020)

dw1305 said:


> I use the health and colour of a floating plant (so not CO2 or light limited) to give me a <"visual indication of nutrient status">. I called this the <"Duckweed Index">, and _Limnobium_ is a nice leaf green colour.OK so you can't add any more fish.
> 
> 
> cheers Darrel



Re the duckweed index, how quickly does the colour change occur when there are insufficient ferts in the water column, and when you do dose, what do you dose with? Asking as I’m considering using this approach to manage my fertilisation regime.


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## dw1305 (28 May 2020)

Hi all,





hypnogogia said:


> Re the duckweed index, how quickly does the colour change occur when there are insufficient ferts in the water column, and when you do dose, what do you dose with? Asking as I’m considering using this approach to manage my fertilisation regime.


Within a couple of days, or quicker, for all the mobile nutrients. With nitrogen you get almost instant greening.

The only real problem is with the non-mobile elements, so in practice really just iron, because the plant can’t move nutrients to old leaves, and it’s only leaves that grow after iron becomes available that are green.

That was one advantage of Duckweed (_Lemna_ _minor_) it has very quick turn over of fronds, so shows a quicker response than Amazon Frogbit (_Limnobium laevigatum) to _both nutrient deficiency and nutrient availability.

Cheers Darrel


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## dw1305 (29 May 2020)

Hi all,





hypnogogia said:


> and when you do dose, what do you dose with?


Have a look at <"Why add fertilisers....."> and <"linked threads">.

<"Frogbit taken a turn"> might also be useful.

cheers Darrel


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