Watering a cactus with fish tank aquarium water?

[BassetsforBrown]

I have a large columnar cacti in my house just about to come out of dormancy, it's been 3 months since it's last watering so going to give it some water. I also have a 90 gallon fish tank that needs weekly water changes. I know many other plants can benefit from the fish tank water because it has a lot of dissolved nitrates from the fish poop. Is this also true for succulents? Or should I stick to regular purified water?

[adetheproducer]

No, to much organic matrrial. It is likely to cause fast growth and split the cacti or attract fungi and rot. Usually for cacti you would want fertilisers with low nitrates and high potassium and phosphorus and only used very sparingly. Fish thank water is too full of nutrients.

[CactusFanDan]

Yeah, too much nitrogen. You'd end up with bloated, flabby plants. Save your tank water for growing lettuce or something leafy.

[Carl_B]

also don't water house plants it will smell of old fish tank... I used ex aquarium gravel in some of my soil mix last year, greenhouse smells rank when I water

[Saxicola]

I disagree with the other comments. I used to water plants all the time with fish tank water and I wouldn't hesitate to do it in your situation either. If you have a healthy nitrogen cycle going on in your tank the level of nitrates won't be bad. The level of nitrates will be below what a normal full strength fertilizer is at and succulents can handle full strength fertilizer just fine (it is an old wives tale that has been perpetuated that cacti and succulents can only handle very low nitrogen). The only real risk would be overwatering your plants if you did it too often, but that is true of tap water as well.

[BassetsforBrown]

My tank has been fully cycled for over a year, zero ammonia, zero nitrite. Everything is fully converted into nitrate. As far as over watering, I'm not worried, it's been inside and dormant since the end of September, and I've only watered it twice in that time. During the Summer I keep it outdoors - I live in MA so the winter would kill it

[Tony]

I agree with Saxicola. I used aquarium water to water cactus seedlings for a few years. The water I used never caused bloating or any other negative effects. In fact, I stopped using it because I got far better growth using Acidified water with 1/4 strenght fertilizer added.

Why do you need to change the water once a week? Raising discus?

I have a 100 gallon south american community tank that gets 25% about three times a year.

[CactusFanDan]

I agree with Saxicola. I used aquarium water to water cactus seedlings for a few years. The water I used never caused bloating or any other negative effects. In fact, I stopped using it because I got far better growth using Acidified water with 1/4 strenght fertilizer added.

Why do you need to change the water once a week? Raising discus?

I have a 100 gallon south american community tank that gets 25% about three times a year.

Back when I used to keep fish, the consensus seemed to be that you needed to do some kind of water change every one-two weeks. However, thinking about it logically if you have a good, adequately sized filter and your tank isn't overstocked then I don't really see why you'd have to change so frequently. Probably a matter of opinion and preference, but I don't think it's 100% necessary. Having a planted aquarium helps to soak up nitrogen and other waste products too.

[promethean_spark]

I had planted aquaria, had to ADD nitrates (KNO3) and other fertilizers because the plants consumed more than the fish did. Still did regular water changes though, keeps any bad stuff from accumulating. I had a whole automated system for doing water changes. I moved and the new house had new hardwood floors (the angelfish died in the move...), so the tanks went in the garage and the lights went into the propagator.

2005 - RIP.