Black skirt tetra's frightened when light's on

[Mednes]

So as the title says, I have a fish tank with 6 zebra danios, 1 black molly, 6 black skirt tetras and 2 albino black skirts. They all get along fine, the molly sometimes chases them around but not too much.
The danios and the molly are always lively and swim around the tank, but the school of tetras is always hidden in their corner.

The interesting part is that as long as the fish tank light is off, the tetras are spread all around the tank, too. It's only when the light's on that they retreat to their hiding place.

Any idea why this would be and what to change so that the fish feel more comfortable? Thanks in advance

I would also like to mention that my tank is at about 80% fish saturation, I'm not sure how many gal it is atm. The tank's fully cycled and has been running for almost a year now their behaviour has always been such that they would hide. I also do water changes, but not every weak. I do about 30-40% changes every 2-3 weeks.

Thanks in advance

 

[FreshyFresh]

How do you know your tank is at "80% fish saturation" when you don't know the size/gallons of the tank?

Your black skirt tetras might me avoiding the molly or other aggressors. Maybe increasing the school size of the tetras might work, or having more space and/or decor would calm them.

Welcome, by the way!

 

[Thyra]

Welcome to the forum. In case you have forgotten the formula just measure the length, width and height of your tank in inches and divide by 231. (There are 231 cubic inches to a gallon)

 

[Mednes]

I knew the size of my tank, I just didn't know the size in gallons. I did the maths and it's a ~16 gal.

They definitely could be avoiding the molly, especially because they are pretty much the only ones to ever get chased - the molly completely ignores the danios. Thing is, even if they aren't asleep and other light source is on (the room light is on) they will be out of their hiding spot swimming about. After turning the fish tank light on they start moving towards the hiding spot, not in a panic, but slowly just inch there.

Uhm I suppose they might still be asleep with the room lights on but I don't think so.

Thanks for the welcome, guys

 

[FreshyFresh]

That is quite a lot of fish for something under a 20g IMO. Could you possibly re-home the molly to see if that makes a difference?

 

[Mednes]

I tried putting the molly into a very small separate tank without filtration or anything for the moment, and the fish already seem to be sticking out a bit more. It's definitely not a permanent solution, and I really really like the molly and I don't have anyone to give it to or a different tank to keep it in...

 

[Newman]

that's not doing justice to the molly then. you can't upgrade to a bigger tank for all of them?

 

[FishDad]

When and where did you buy the Molly. Maybe you can return it. Or by another 20 gall stated. They're not that expensive.

 

[Mednes]

Thanks for the replies, guys. I don't know if the tank is overstocked, perhaps it is. However, I've added a few new tall plants into the aquarium, and the fish seem much happier now, as I suppose they can stay well hidden in between the plants. The most of the school is sadly still in the corner, but I think I'll just leave it is it is right now. I mean, I think they all should be reasonably happy now, and when I get more money I'll get a bigger fish tank.

 

[Newman]

if you can upgrade eventually i think it should work out

 

[Mednes]

if you can upgrade eventually i think it should work out

Is that your fishtank in your avatar? It's absolutely gorgeous!

 

[Newman]

yeah my 40 gallon used to look like that while it was fully planted. now its different. it only has a couple of sword plants and large pieces of driftwood.