Used fish tank water okay for watering orchid?

[soundtweakers]

Hi, I have a few Amazonian biotope style planted aquariums that I change water on the weekly basis(about 30 gallon removed weekly). Here are some of the parameters of the used fish tank water.

-Temp 82F
-PH between 6~7...slightly acidic
-GH low, the general hardness is low right out of our
NYC tap.
-Chlorine/chloramine/heavy metal removed by consumer aquarium water conditioner, no chemical added.
-used tank water contains a good amount of phosphate/nitrogenious waste(Nitrate) from the fish waste which are good fertilizer for aquatic plants, but not sure about Orchid.

Would anybody recommend I use this water for my Orchid?

thanks in advance and here is a pic of my tank

[Ray]

Absolutely!

Don't forget, however, that is will not be a complete source of nutrition for your orchids, so you will need to feed periodically.

A couple of comments about NYC tap water and orchids: That is some of the purest water out there, so you will want to use a fertilizer designed for use with pure water, not they typical, mineral-laden tap water seen elsewhere. The tank water pH is almost perfect for the plants, but if you add an off-the shelf "tap water" fertilizer to it, the pH will likely drop too low.

[Donald]

Greetings from Massachusetts. You should be OK. I have a small fish pond that I use the water for my orchids during the summer and they seem to like it. I actually have some native lady slippers in it and they thrive. Have fun.

[soundtweakers]

Originally Posted by Ray

Absolutely!

Don't forget, however, that is will not be a complete source of nutrition for your orchids, so you will need to feed periodically.

A couple of comments about NYC tap water and orchids: That is some of the purest water out there, so you will want to use a fertilizer designed for use with pure water, not they typical, mineral-laden tap water seen elsewhere. The tank water pH is almost perfect for the plants, but if you add an off-the shelf "tap water" fertilizer to it, the pH will likely drop too low.

thank you so much for the advice
I've been keeping fish tanks for over ten years in NYC so I know a bit about the NYC tap water and very fortunate to have good quality water. Do you recommend any particular brand/source of the proper fertilizer to be used with NYC water? I have a bottle of Shultz Orchid Food that I rarely use it due to all the warnings of over-fertilizing, even when I do use it, I do a 1/4 dose. Do you think this will suffice?

thanks again for your help

[Ray]

Hah! You hit one of my "hot buttons"! "1/4 dose" is meaningless. If you want to really know what you're up to, think in terms of measurable units. I recommend 125 ppm N as a standard fertilizer dosing rate (divide 10 by the %N on the label to determine teaspoons per gallon to use).

That, unfortunately, has little- to nothing to do with managing the pH. The two most widely used fertilizers for pure water are Peter's Excel Cal-Mag Grower formula, and the Greencare "Orchid Special for RO", which is what I use, recommend (and sell).

A lot of it has to do with the ratio of nitrate- and ammoniacal nitrogen in the formula. For normal hard water, the dissolved mineral buffering eliminates the issues so can use the cheaper (ammonium) raw materials, but in soft water, you have to control the pH in the formula.

Schultz Orchid Food is higher in ammonium- than nitrate compounds, and also has urea, for which there is some debate if orchids can even absorb it directly.