Unexplained Blue Water (Not The Shopping Centre)

[Roy's Mum]

Hello

Not really sure where to put this, not *that* new to fishkeeping, but after the initial tank setup hiccups, haven't had to ask for a lot of help, so I suppose new in that sense.

I've seen several posts about this but none actually seem to get to the root of the problem (or post about it if they do), so please excuse any duplication. I've tried to cover all common questions to see if anyone can help with anything that hasn't been previously mentioned. Here we go...

One of my tanks (36l, mollies, ornaments and plastic plants) water has turned bright blue, as if it has meth blue treatement in there. It doesn't.

It's not my tap water.
The water is turning blue in the tank.
There is no slime or anything, so I don't think it's cyanobacteria(?)
There doesn't seem to be anything else wrong with the water, i.e. it's not cloudy, etc.
It doesn't get lots of natural light, in fact it gets little.
I've got an LED light which is on for about 5 hours a day, I can alter it but at the moment it's just a normal sort of white light, no blue tinge as I don't like that particularly!
I've tested the water myself and so has the local aquatics place and they can't suggest what's going on or find anything wrong.
The fish seem perfectly fine.
It's nothing close to the tank that is blue or green making it look blue when it isn't.
There hasn't been a treatment in the tank for probably a year at least.
There's a blue sponge in the filter but that's also been there for over a year, no idea why it would start leaching colour now.
The gravel is regularly vac'd.
The ornaments are cleaned every couple of changes.
I've removed any ornaments with blue paint on and that doesn't seem to change anything. None of the other ornaments or plants are blue or have been a problem up to now.
I'm using Aquacare Tap Water Conditioner and Stability, and a low salt dose (1g per litre) for molly health.
My second tank (planted, no ornaments or plastic) has none of these issues and is treated more or less the same (without the salt).

The only thing the aquatics place could suggest was putting a carbon filter in there to see if that helped clear it, which I've just done so too early to say if it helps, but I'd rather get to the bottom of what's caused it if I can.

Any thoughts that aren't covered in the list above? I'm baffled.
Thanks in advance.

[Martinspuddle]

Blue water? I was thinking what on earth ...I get confused easily these days.

Three questions:

Your aquariums water parameters?

Your local water supplier?

Any pictures of aquarium and a simple of this water.

In the mean time might be prudent to purchase a geiger counter!

[black ghost]

So you’re removing it with water changes, and then it turns blue again?
Possibly the blue sponge. Blue treatments absorbed by silicon can be released but I doubt it would be that much, and suddenly after more than a year...

[Roy's Mum]

Water parameters - ammonia and nitrite 0, done with drop tests, and nitrite plus whatever else is on the dipsticks all in the green zones. Temp was a wee bit low (22) as I haven't had the heating on this week but usually about 24.

Water supplier is Northumbrian. Do they publicise anywhere if they change anything?

Pictures I will try again tomorrow in daylight as I'm not getting an accurate representation with my crappy phone.

You can't really see it's blue in a 5ml sample test tube, but a litre in a white bucket is enough to see it's blue. It's almost like someone has splashed some mouthwash into it, it's that sort of blue (but no, I haven't, and if I had I'm sure it'd smell minty )

Yes, I'm basically at the beginning of small daily water changes plus the carbon filter to see if that helps. If you think it really could be the sponge I'll try getting a second one bacteria'd up alongside it for a while and then swap them, and see if that helps! Seems unlikely given how long it's already been in there but it's worth a shot!

Thanks

[fr499y]

Do you have a storage tank by any chance? When water has been sitting in old copper pipes/tanks it can turn a very slight tinge of blue.

Do you have a copper test at hand?

[Roy's Mum]

No, no storage tank. I think some of our pipes are copper, but they've always been so again, no idea why it would start recently.

[black ghost]

Sponges degrade eventually. It makes sense to me that it could start after a long time.

[Martinspuddle]

Do we know how old this blue sponge is?

[plankton]

Just over a year seems pretty early to me for a sponge to start breaking down, unless it was in storage for several years previous to sale.

[Roy's Mum]

Yeah, it's only about a year old. I think I'll try to replace it anyway. It's the bluest thing in there so won't hurt!