Zeroing in on nitrate-free plant food: what are your options?

[LacieB]

I've always run my tanks with CO2, but not consistently, and I've had decent results with low-light plants. My nitrate levels are usually around 40 ppm, and I do a monthly water change. My fish are thriving, and the anubias seems to love it.

I'm having some trouble getting my 29-gallon tank's nitrates below 40 ppm - I did a 50% water change last night, so we'll see if that helps. My 55-gallon tank is at 10 ppm, and the hex tank is doing fine, but I'm not really sure what's going on with that one.

From what I've learned, plants need nitrates to grow. I'm not looking to break the bank on plant food, but I do have some muriated potash lying around - I'm thinking of adding a small amount to my 55. I've also got Activate and Envy for my plants, and I recently picked up Flourish Excel, but I haven't used it yet.

So, what do you guys use for plant fertilization? I'm looking for something that'll work with my sketchy CO2 setup - I've got a 20 lb canister for keeping SHB out of my Lioneycomb, but it's not exactly designed for indoor use. I've also got relatively low nitrates and low light, so any suggestions would be appreciated.

[angelica]

Aquatic plants actually prefer ammonia as a nitrogen source - they only resort to nitrates when ammonia's not available. My experience is a bit different from yours, LacieB - all four of my tanks have zero nitrates, and I attribute that to the fish providing ammonia that the plants use up before my filter can process it. This setup seems to work in my favor, as my nitrates are still zero right before my weekly water change.

Now, I'm aware this approach has its downsides - my filter bacteria are probably starving due to the lack of ammonia to process. On the other hand, I don't have to worry about my filter crashing, since it's mainly used for circulation and mechanical filtration.

[coltin]

It's worth checking your tap water for nitrates. You'd want to keep those as low as possible for the long-term health of your fish. Ideally, you're looking at 0ppm nitrates, and less than 20ppm at all times.

Regular water changes are key to keeping nitrates down. I'd recommend doing them more often to keep those levels in check.

Adding CO2 or large amounts of fertiliser isn't necessary unless you've got a tank full of fast-growing aquatic plants and only a few small fish, with plenty of light. There's already plenty of CO2 in the average aquarium, produced by the fish, filter bacteria, and the atmosphere.

I'd advise against adding garden fertilisers to an aquarium with fish, shrimp, or snails. Not a good idea.

Anubias are slow-growing marsh plants that won't do much to control nitrates. If you want to reduce nutrients, floating plants like Water Sprite, Duckweed, or Salvinia are a better bet.

In my plant tanks with lots of light, I used an iron-based liquid fertiliser and terrac in the gravel.

[LacieB]

I want my biological filter to have some oomph, that's why I use undergravel filters - like Fluxx. I'm a fan of crystal-clear water, and I like knowing my filter can handle a sudden influx of fish. So, I'm not sure I want to aim for zero nitrates if it means my plants are doing all the work and my filter is basically useless.

I went down the "zero filter processing" road in saltwater back in 2003, and it was a disaster. I ditched my undergravel and canister, switched to sand, and added extra pumps to blast water at my live rock. The result? A dead yellow tang and a tank that was a total pain to maintain. I ended up going back to my trusty undergravel and canister, and life was good again - until the water changes started getting too much for me.

[boomer]

When it comes to nitrates in aquariums, I think we need to look at it from two angles - the health of our fish and the preferences of our aquatic plants.

First off, fish health is a top priority. In their natural habitats, tropical fish aren't exposed to high nitrate levels - if at all. I've never come across readings of even 1 ppm nitrate in their natural habitats. It's clear that our fish will be healthier with zero or near-zero nitrates. Some fish, like cichlids, are particularly sensitive to nitrates. The thing is, nitrates can weaken a fish's physiology, making them more prone to other issues that they'd normally handle with ease. So, if you want healthy fish, keep nitrates as low as possible - definitely below 20 ppm.

On the plant side of things, most aquatic plants prefer ammonia or ammonium. They'll readily take it up, and faster-growing plants will absorb more. Floating plants are great at this - they're often called "ammonia sinks" for a reason. I've learned from Tom Barr that it's almost impossible to overstock a tank with fish to the point where the ammonia isn't taken up by the plants, assuming you've got a decent number of them, including some on the surface. This applies to low-tech setups too. High-tech with lots of light and CO2 is different, but in those cases, we use nitrates because plants need to convert them back into ammonium to use them. It's clear that plants prefer ammonia and only resort to nitrates when everything else is available.

Now, nitrates can come from two sources - the fresh water we add during changes or the biological system itself. If the tank is properly stocked, not overfed, has live plants, and receives regular water changes and filter cleanings, nitrates from the biological system shouldn't be an issue.

[TwinTankman]

Aquatic plants actually prefer ammonia as a nitrogen source - they only resort to nitrates when ammonia's not available. My experience is a bit different from yours, LacieB - all four of my tanks have zero nitrates, and I attribute that to the fish providing ammonia that the plants use up before my filter can process it. This setup seems to work in my favor, as my nitrates are still zero right before my weekly water change.

Now, I'm aware this approach has its downsides - my filter bacteria are probably starving due to the lack of ammonia to process. On the other hand, I don't have to worry about my filter crashing, since it's mainly used for circulation and mechanical filtration.

I think there's a bit of confusion here. Aquatic plants don't directly use ammonia, they use ammonium. The bacteria in the tank are the ones that take care of the ammonia. What's interesting is that plants actually provide a home for the nitrifying bacteria on their stems and roots. And when those roots are in the anaerobic zone, some plants even release oxygen to help the nitrification process along.

The thing is, plants can consume ammonium way faster than the bacteria can take care of the ammonia. But both are present in the tank, working together. It's almost impossible to have live plants and no nitrifying bacteria in a tank. On the other hand, it's definitely possible to have a tank with no plants or algae, where the bacteria are the only ones processing the ammonia.

[shakinStevens]

I've always run my tanks with CO2, but not consistently, and I've had decent results with low-light plants. My nitrate levels are usually around 40 ppm, and I do a monthly water change. My fish are thriving, and the anubias seems to love it.

I'm having some trouble getting my 29-gallon tank's nitrates below 40 ppm - I did a 50% water change last night, so we'll see if that helps. My 55-gallon tank is at 10 ppm, and the hex tank is doing fine, but I'm not really sure what's going on with that one.

From what I've learned, plants need nitrates to grow. I'm not looking to break the bank on plant food, but I do have some muriated potash lying around - I'm thinking of adding a small amount to my 55. I've also got Activate and Envy for my plants, and I recently picked up Flourish Excel, but I haven't used it yet.

So, what do you guys use for plant fertilization? I'm looking for something that'll work with my sketchy CO2 setup - I've got a 20 lb canister for keeping SHB out of my Lioneycomb, but it's not exactly designed for indoor use. I've also got relatively low nitrates and low light, so any suggestions would be appreciated.

This is actually not correct. Plants need Nitrogen (N), not nitrates (NO3). However, potassium nitrate is the easiest to find and is less toxic than ammonia or nitrite. So many fertilizers use it. One alternative is Urea, CO(NH2)2.

I've used it in my tank successfully. I've also read of others using it successfully. My understanding is that seichem nitrogen is mostly Urea with some KNO3. But there is a hazard that it could convert to ammonia. I haven't seen that in my aquarium. Possibly because the plants consumed the ammonia before I ever noticed it.

If you have measurable nitrate, you might not need to add it for plants. Is the nitrate coming from your fish or tap water?

Considering your post, LacieB, I'd say be cautious with adding just one nutrient, like Potassium. Plants will use the potassium and the other nutrients in the water, then stop growing because of multiple deficiencies. You need all the nutrients.

A cost-effective way is to only use the amount necessary. Anything over what's needed is wastefully spent. For a 55-gallon tank to achieve 10ppm NO3, you need about 3.3 grams of KNO3. A one-pound bag of KNO3 costs about $4 on a mail-order site. That's enough for 151 10ppm doses done once at each water change. That's enough for seven years. The best way to dose a fertilizer is to use a fertilizer calculator to determine how much to add and then measure it out and add it.

If you buy a liquid fertilizer, you'll end up spending a lot of money for mostly water, and there's no guarantee the company is making a good product that will work in your tank.

Another way is to use the waste from your fish to fertilize the water. This involves fewer water changes, so fish waste builds up to allow plant growth. However, this involves some risk since stuff other than plant nutrients can build up and become toxic. This has been used in larger tanks like your 55-gallon but is difficult to do in smaller tanks.

You might want to try a floating plant first, like Salvinia or red root floaters. If these grow without evidence of a nutrient deficiency, like yellow or damaged leaves, you might already have enough nutrients for some plants. If the plants don't look good, it might be possible to figure out what nutrient is missing and adjust for that.

At this point, it all depends on what you want to do. But there isn't enough information in your post about what you want.

[LacieB]

Thanks for the info. I'm looking for a low-maintenance setup without the hassle of cyanobacteria or problem algae. I considered adding potassium initially to combat the red cyano I had, but I've since reduced the light - swapped out the bright LEDs for a fluorescent fixture, cut back on feeding, and gave the tank a good cleaning. I'm pretty sure I've got the cyano under control now, but just in case, I moved my albino pleco to another tank. My main goal is to enjoy my fish and have a tank that can thrive even when I'm away for 10 hours a day during spring and fall. I've always relied on undergravel filtration and never really fertilized my anubias and java - the fish provide the CO2 and nitrates. I'm not looking for a showpiece tank, just one that'll stay healthy and happy with minimal fuss.

[coltin]

I wouldn't add anything for Anubias or Java Fern. They seem to do just fine on their own, and I've had them for a while now without any issues.

To keep Cyanobacteria away, I've been focusing on keeping the tank clean. I've also been considering adding some floating plants to help reduce the occurrence of BGA. I've heard that floating plants can really help with this, and I've already seen some improvement since I made a few changes to my tank. I reduced the light, switched to a fluorescent fixture, and cut back on feeding. I also did a good cleaning of the tank and moved my albino pleco to another tank just in case.

[LacieB]

I've got some crypts in there, I think, and that's why I added the fertilizer pill. I've kept Anubias for years without fertilizing, just feeding the fish and doing a monthly water change - I know, it's not ideal. But I've never had a problem with blue green algae, and it seems like all I'd need to do to get it is add a piece of limestone - our pH is already high around here, and the lime leaching just pushes it over the top.