Nitrate Deficiency?

[jn]

Hi there, I recently did some nitrate testing in my pond. The nitrate reads zero. I doubted the test but confirmed it was genuine when I tested my tap water (which tests at about 10ppm)

Whats the best thing to do here? Some of my plants are beginning to go slightly yellow. The plants are in baskets of gravel.

Other parameters are fine, no nitrites or ammonia, pH is stable around 7.4. There's a very small amount of blanket weed which is too small to remove. I have been doing 10-20% water changes weekly and keeping the bottom clean with a syphon (it's a larger than average barrel, holds about 200L so pretty small).

Currently stocked with 4 small goldfish (total about 7 inches and growing, I'm hesitant to add fish as I'll have nowhere to put them when they outgrow the barrel.)

This is a still pond, no circulation or filtration. Just plants. Should I change less water or leave more gunk in the bottom and see if I get a buildup? Should I just do more water changes to keep adding nitrogen from the tap water?

Any advice would be appreciated thanks!

[alanmin4304]

If you have heavy root feeding plants they will require food in the pots rather than in the water. You may be better to add food to the pots to feed the plants rather than to the water which will feed the algae.

[jn]

Thanks for that.

Anyone know if aquarium fertilizers would be much different to pond fertilisers and which types/brands might be better value or performance wise?

Actually, my yellowest plant is a large basket of lsymachia thats sitting about 10cm below water level. It's not the 'aurea' cultivar.. was definitely green. Are they heavy feeders?

The others are ranuculus lingua, lilaeopsis (n.z), and gratiola sexdentata.

(actually.. Caryl has these same plants in her pond and has recently added photos in another thread)

Wish those fish would hurry up and grow.

[purplecatfish]

Yellowing can sometimes be caused by trace element deficiency such as iron. But in this case it's probably lack of nitrogen and you might be able to add more fish .

I fertilise with liquid potassium which is sometimes the limiting nutrient to plant growth. More Potassium helps the plants to use the available Nitrates (and also starves algae) so that I often get very low nitrate levels considering the number of fish in my tanks. The plants then act as a sink for the nutrients/fish waste and then are likely to need constant pruning or thinning out.

I wholeheartedly agree with Alanmin4304's comment re root feeding. Most plants except floating plants will derive much of their trace element needs from their substrate so feeding the water makes those nutrients available to algae as well whereas poking fert pellets into their basket makes them available to the plants before the algae can get a look in.

The test from my 5ft tank this weekend was zero ammonia, nitrite and nitrate, 5KH (hardness) and a pH of 7.2 (unusally high for this tank). I've been double dosing with Flourish excell and adding Seachem's potassium daily. My plants include twisted val which is known by some to melt from the Flourish excell, however mine doesn't.

[alanmin4304]

I was in that place in Bleneim Rd today which sells fountains/water features and plants etc. I think it is called the water garden. They had tablets on the counter for water plants. Someone else may know how good the are.

[jn]

Thanks guys.

Alanmin..I know the stuff you mean.. "pond tabs".

I actually just put some into a pond at our rental place cause there are a fair number of water lilies in there which will no doubt be really big feeders (nitrates are nil in there too although everything still looked very healthy!). First time using them. I'll see how they do there. That pond is about 1100L with 8 fish 5 water lilies and a bunch of pretty big marginals so i figured it would be more tolerant of some extra fertiliser than my 200L job.

I can't find the N-P-K details for pond tabs though? Very paranoid about adding phosphorous. Does anyone know?

Where do you get liquid potassium? Is it an aquatic thing or just some generic stuff?

[jn]

Found it... PONDTABS 10-14-8. Seems alot of phosphorous. Maybe I'm just too paranoid? :-? Blanketweed really sucks though!

[purplecatfish]

You can get Flourish Potassium from your LFS. But I'm trying to find some Potassium Sulphate or similar potassium product to make my own liquid feed.

Is there someone who is doing this already, or maybe one of those people who makes PMDD (poor mans dosing drops) could tell us where they get their chemicals? And what the actual potassium content is?

[alanmin4304]

You may get what you want from hydroponics supplies

[Blackadder]

How much Potassium salt are you after?

[purplecatfish]

I've got aprox 1250L of planted tanks which I've been adding fert daily, so quite a bit I guess.

I've tried the local hydroponics store but they only have standard plant products with phosphrus in them which would lead to algae problems.

[davidb]

try a chemists- I believe they have online websites and the like. By chemists I mean chemistry, the science not the drugstore people

[jn]

Hey purplecatfish, Found this website today:

http://www.csd.net/~cgadd/aqua/articles.htm

There's a fertilizer dosage calculator (second item on the page) that looks extremely handy. Sounds like Potassium Nitrate could be handy for me. Could be handy for you too? There's also a calculator for Potassium Chloride and Potasium Sulphate so I guess those are compounds that are readiliy used.

I found a website (hydroponics.co.nz - see bulk chemicals) that was selling 1kg of Potassium Nitrate for ~$6. (I also don't know how harmful sulphates or Chloride would be in the water so Potassium Nitrate sounds like a safer bet!) They also stocked Potassium Sulfate but not Potassium Chloride.

Unfortunately shipping doubles the cost but I think I'll try to find some locally. Found a few hydroponics places in chc in the yellow pages.

Since both the pond at the rental place and my barrel pond are at zero nitrates it could be handy for me to get familiar with a supplement.

I found a website too that said my lsymachia is often used as an 'indicator' plant for nitrate levels! Said it loses colour when nitrates drop below 5ppm. Even my liliaeopsis is yellowing so I'd really like to fix it.

Can you buy potassium test kits? Is it possible to have too much potassium and would any of this have any effect on pH? (Can't imagine that it would but pays to ask I guess!)

Oh.. my fish were really 'chasing' this morning so with any luck the population will be on the increase! Yaaay!

[alanmin4304]

I would have thought pot nitrate would be pretty difficult to obtain with its other uses.

[Blackadder]

I can probably get you some, do you want the Nitrate?

[evilknieval69]

http://www.hydroponics.co.nz Good store, good people to deal with, very efficient.

[purplecatfish]

Thanks for the recommendation evilknieval69 .

They do provide a great service, and I'll be saving hundreds of dollars over the year .

I've been using the potassium sulphate and I've also got some potassium nitrate from them.