The Puffer Forum

My saltwater aquarium has a beautiful light blue tinge to the water. The kind of blue you would see in crystal or a diamond. Is this normal? This is my first SW tank, so I'm not sure if it would be the same as FW. My FW tanks never had this color before. I can only see this color when I look through the aquarium length ways and only when the aquarium lights are tuned off during the day when natural light is hitting the aquarium. The water is crystal clear and everything it just had a slight light blue color to it. Ammonia 0, nitrite 0, nitrates 3-5, pH 8.3, SG 1.023. It is a 33 gallon FOWLR tank with a zebra hermit crab and 2 balloon mollies. Prizm protein skimmer, 40-60 gal hang on back style filter along with a fluval 205 canister filter. Has been up and runnig for about 2 months. Fully cycled. Is this color normal? Thanks.

i believe this is normal. other factors affecting the color you see when looking lengthwise is the composition of the glass. i would say very few of us out here have any control over what goes into the glass used for our aquaria.

yap.

My marine tank is a clear blue, my FW. is a tinge of green (probably algae)

Starfire glass and its similar compositions are low-iron glass an are far better at producing blue-looking water, as they are made with low-iron materials. Conventional aquarium glass has a non-trivial iron content, so appears green. You can see this easily by looking at the narrow edge if the glass at the seams. Low-iron glass is significantly more expensive, so is only found in more expensive tanks. The two forms do have a subtle but visible effect on the water appearance. Master aquascapers prefer to use the low-iron glass because you can see the difference in person and in photos. By itself, it will not change the color of the water, but if you have diatom-filtered the water anyway pre-photo, the low-iron glass will look better and bluer in the pictures and in person.

I would think the actinic lighting would make the water appear blue. That's what I've always assumed in my tank.

You can see this easily by looking at the narrow edge if the glass at the seams.

So I'd be looking for a bluish tint in the glass?

it also depends on the lights.

lights range from 3k (yellow) ~ 20K+ (blue) as you go up the spectrum the more blue it looks.

do a quick search on "redshift blueshift" if you are interested in light, time and space. Cool stuff

Glass with normal iron content looks green edge-on, low iron or iron-free glass looks blue. Very easy to see. That test still works fairly independently of the tank lighting. High actinic levels make everything look blue to me, But if you check the glass edges you can still read low-iron versus standard glass.

So far as I know, Oceanic really pushed the low-iron glass in the hobby some years back. Now multiple lines offer such. It is $$$, but you can see the difference if you have both types of glass closely placed. It makes glass look like good acrylic for color rendition and transmission, without the distortions or sensitivity to scratches.

In the interest of fairness - I have to admit that I am not a fan of plastic tanks. I started SW with acrylic tanks, but back then they were all custom and used much thicker panels. Good glass tanks can be forever. Plastics are not, and current production models show too much distortion for me. i won't have them in the house.

Hmmm... the one on my reef tank is blue.

Then it is likely low-iron. That gives better color visibility. Your reef certainly shows off quite well!

I bought that tank used, from a "well-off" woman.

That may be the trick. That was a good buy, and boy have you done a nice job with it, it is spectacular!