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FAQs on Freshwater Aquarium Phosphates

Related Articles: Freshwater Aquarium Water Quality, pH, alkalinity, acidityTreating Tap Water, Freshwater MaintenanceFrequent Partial Water Changes Establishing Cycling, Freshwater Filtration, Setting up a Freshwater Aquarium, Tips for Beginners

Related FAQs: FW H2O Quality 1, FW H2O Quality 2, Aquarium MaintenanceTreating Tap Water for Aquarium Use, pH, Alkalinity, Acidity, Water Hardness, Nitrogen Cycling, Establishing Cycling 1, Ammonia, Nitrite, Nitrate, Freshwater Algae Control, Algae Control, Foods, Feeding, Aquatic Nutrition, Disease


Re: Empire State of Mind - FW soft/hardness, and HPO4, algae...  2/1/2010
Thanks a lot for your input, Neale!
<Happy to help.>
After a lot of tinkering, I have created my own cichlid salt mix where one teaspoon added to a 5 gallon bucket of de-chlorinated tap water creates water with 3-4 KH, 8 dh a PH of about 7.4.
I would have liked to get the KH slightly higher, but adding relatively more baking soda to the mix increases my pH too much (I don't want to go above 7.5 for the kinds of fish I currently have/ will have in the future).
<I agree.>
After doing more reading on water chemistry, I became more aware of the importance of phosphates.
<No importance at all, in freshwater systems anyway. Why are you worried?>
I don't own a phosphate kit yet (ordered one, but I also read that many kits only test for organic phosphates, anyway), but the New York water utility states that our tap water contains about 2 mg/l (Ortho-) Phosphates, described as "Water additive for corrosion control". I have battled green algae blooms in the past, but after leaving the lights off for a week and then adding more fast growing plants, I seem to reached an uneasy equilibrium (water definitely looks more greenish than in my quarantine tank, but I don't get full-blown blooms).
<There's little evidence phosphates have anything to do with algal problems. Do read here:
Most algal problems come down to lack of fast-growing plants and the wrong type/amount of light.>
So here is my question: Assuming that my water does contain 2 ppm, would the (Ortho-) Phosphate act as a buffer in my still close to 0 KH water?
I tried to find more info on phosphate based buffers, but couldn't determine the answer for certain. My worry is that if I start aggressively removing phosphates in an effort to get extra-clear water, my pH might crash. What do you think?
<Above pH 7, the effects of phosphate acids are unimportant; it's really down to carbonate and bicarbonate.>
Thank you so much!
P.S. I did read the FAQ's on phosphate in fresh water etc, but didn't seem to find the answer.
<Because no-one cares! Cheers, Neale.>

Re: Empire State of Mind - FW, HOP4, algae    2/1/10
sounds good. I was worried about phosphates because I read in numerous places (incl. WWW) that phosphate levels at 2 ppm or higher often result in algae problems.
<In the past this was often supposed. Indeed, even now, the precise causes of algae "problems" remain obscure, and mostly you hear opinions rather than fact. At face value, yes, in the WILD, eutrophication of water bodies,
i.e., rapid increases of nitrate and phosphate levels, does usually lead to algae blooms. Sometimes these are natural, as in upwelling areas of the sea, and sometimes man-made, as when agricultural run-off gets into lakes and rivers. But broadly, yes, there is a connection. However, the problem with applying this to aquarium conditions is that an aquarium isn't a comparable system. There are plenty of aquarists with tanks that have high nitrate and phosphate levels, and yet no algae problems of any kind.
Conversely, some people constantly wrestle with algae problems despite very low nitrate and phosphate levels. So there are other factors at play. What the whole Amano trend towards planted aquaria has revealed is that fast
growing plants do, somehow, prevent algae problems. Some argue it's about nutrient uptake, others the plants cut out light, and yet others that there are allelopathic effects between plants and algae. It may be a combination of all three. But certainly, stick a big clump of Indian Fern in a messy cichlid or catfish tank, and algae stops being a problem, assuming light intensity is sufficiently bright for the Indian Fern to grow fast.>
I am getting close to upgrade to a 75g with real lighting (have an Eclipse system now, which makes it tough add enough lighting), but wanted to iron out all my water issues before I do. If you think that that my current
latent algae issues are not going to become a full-blown problem once I am using at least 3W/gallon of 10000/6700 light (provided I include enough fast growing plants), I am happy and shall leave my 2 ppm of phosphate alone.
<I agree. Provided you choose your plants carefully, you shouldn't have problems. Floating plants are easy in this regard because you just chuck 'em and let them do their thing, but they can look a bit messy! If you're going with "pretty" plants, then you need to look at things like Hygrophila, Vallisneria and so on. Essentially anything that grows like a weed should do the trick. These tend to be the species adapted to environments with lots of light, and also seem to be the ones that evolved mechanisms to deal with algae that might smother them. Algae magnet species, like Anubias and Java fern, are obviously of no use at all.>
Thanks a lot!
<Cheers, Neale.>

High phosphates/cloudy water in freshwater tank 11/5/08 Hello Crew, <Hi> I have an established 46 gallon freshwater tank with river-style gravel, an AquaClear 110 (just ordered an Eheim Classic 2217 upgrade), various fake plants, resin rock, and a single 36" Tropic Sun fluorescent light (on 8hrs/day). My (currently sparingly-fed) livestock consists of 15 small tiger barbs, 3 pictus cats, and a red-tailed black shark. <Ok> I've had several battles with blooms of suspended algae over the past 6-8 months. Though the blooms have (temporarily?) subsided, I'm experiencing some white/grey cloudy water. <Likely some sort of bacterial bloom.> I recently purchased a phosphate test kit and I'm getting readings of 5 ppm. Ammonia and Nitrite are at 0 and nitrate hovers around 5 ppm or less. <Did something die in the tank perhaps? Some change or additive that is causing your tank to recycle, which the evidence seems to suggest is happening.> I've been doing several water changes each week but I can't seem to drop my PO4 levels (0 ppm from the tap). <What and how much are you feeding? Maybe try another test kit to make sure it is accurate.> I'm taking a ride to the LFS tonight to pick up a Poly-Filter (I heard these work well), but I'd rather remove the problem than bandage it. Any thoughts? <The Polyfilters will help, but as for the cause check your food quantity, clean your filters often, and more water changes. Are you using any other additives?> The gravel was changed about 5-6 months ago, could it have been a bad batch that is somehow leaching PO4 into the water. <Seems unlikely but worth investigating, try soaking some in a otherwise clean container overnight and check the water in the morning to see if phosphates appear.> I don't use any type of chemical filtration, just sponges and bio-media in the filter. If plants are the solution, would that require different gravel as well? (e.g. eco-complete, as opposed to frequent supplementation, etc.) <Not necessarily, in my planted tank I have pea sized gravel, and then just placed a little (handful) of eco-complete (I think, may be a similar product, but not at home at the moment to check) around the planting site. Seems to have worked well.> Any help is greatly appreciated. Thanks, Billy <Plants will help, but I am concerned that more phosphate is being added to the tank, keep testing and try to eliminate and possible sources one at a time to see if you can determine the cause.> <Chris>

Re: High phosphates/cloudy water in freshwater tank 11/06/08 Hello again, <Hi> Thanks for the advice. <Welcome> I don't believe anything has died, but now that you say it, perhaps a full gravel cleaning is in order (maybe it's buried?). <With ammonia reading I would not go too crazy, will destroy your biofilter that way.> I feed very sparingly, it takes maybe 3 minutes for the fish to finish. <Cut this by 2/3s, all food should be consumed within 1 minute.> As far as additives go, I use Amquel during water changes. <This may explain your ammonia readings, binds the ammonia so it never breaks down. Many test kits will still read this as free ammonia.> I've used the water clarifiers in the past (flocculants), but I find that the tank will stay clear for a day or so, then go back to it's original state, so I'm not a big fan of adding "stuff." <Good> I will try your idea and soak some of the gravel overnight. Aside from a possible bacteria bloom, is it possible that the high phosphate content is causing the cloudiness? <Could> Thanks again! <Welcome> <Chris>

Re: High phosphates/cloudy water in freshwater tank 11/7/08 Wow, 1 minute...here I am thinking I feed sparingly. <A common misconception, you are not alone here.> Would you suggest any other conditioner for water changes that wouldn't throw my readings off? Most of them seem to "detoxify" ammonia etc. but it would be nice if they just removed chlorine/chloramine so I could get an accurate reading. <They all work the same way, if you can find out what your water municipality uses you may be able to avoid the need for a water conditioner, unless it is using chloramines.> <Chris>

Phosphate sky high! FW   5/2/07 Hi Crew! I'm stuck at home for a few months nursing a badly broken elbow, what to do with so much time on my hands! <Read? Learn to do things with your other arm?> Typing in a cast is somewhat of a challenge, <Yikes. No fun> oh well, I'm gonna give it a go.  I have been having a small problem with my 55 gal tank and I'm sure you guys can help. It is a heavily planted tank with a total of 250 watts CF 6700K lighting CO2 injection, mix of Fluorite and eco-complete substrate, Marineland magnum 350 canister/ 2 bio-wheels and a sponge filter. Temp is 82F, Ammonia and Nitrite 0, Nitrate is now at 5.0ppm/mgl. I do a 20% water change once or twice a week and always remove uneaten food, which is not much as my Discus love to eat! PH 6.8 - 7.0 Iron levels are testing at 0 even though I am adding SeaChem's recommended dose, but that may be a test kit issue I am pursuing with Red Sea.( I added Iron directly to the test water and still got 0). <Mmm, also check with another source of iron...> Need some advice here, should I get another test kit as Red Sea is not responding to my emails. <I would> My plants consist of 3 large Amazon swords with around a dozen offshoots, watersprite, Cabomba, Indian red swords, micro Swords, several Anubias Nanas, green Windth, Elodea, Java Ferns , Vals and some Duckweed .My ferts consist of Seachem Trace and Iron also Plantabbs from AP. <Good products> I had finally achieved a balance of good plant growth with a minimum of algae. Fish consist of a breeding and continuously multiplying school of (7) Zebra Danios, 3 Oto algae eaters, pair of bristle-nose Plecos, 3 Yo-Yo Loaches some freshwater red and ghost shrimp (which are being moved to a shrimp tank), and my babies, five 3 1/2" Discus. When I set this tank up about 5 months ago my goal was to have a planted Discus show tank. Four weeks ago I finally began purchasing the Discus. The store required a PH of 7.0 for these fish so I was asked to use SeaChem's Neutral Regulator. <Mmm, I'd start with RO...> Several days ago I noticed an increasing growth of black and green hair algae. I checked my Phosphate levels and was shocked to see levels over 10ppm/mgl. <Zounds!> I began doing 25% water changes but soon realized the Neutral regulator was creating the high levels. I did 2 more water changes using SeaChem's non-phosphate Acid/ Alkaline buffers, also removed Carbon and added a Phosphate remover to the filter. Phosphate was still over 5.0 this morning. Usually it's .25 - .5 since my tap water is .25. Even though I know phosphate is not dangerous for the fish, <Can be indirectly... by fueling mainly algae populations... their consequent metabolite effects...> I would like to see it much lower. The algae is gettin out of control...again! Are there any quick methods to reduce these levels (water changes are a bit difficult with one arm). Should I add other macronutrients to help the plant use the available phosphate, <Mmm, I would NOT, if you have reasonable, desired growth already> What effect does CO2 have? <Mmm, is an essential nutrient, as well as a "provider" of conditions that allow other nutrient uptake...> Which plants are best at using phosphate. <Mmm, ones that are rapid growing...> Thanks for your time, Bob Bowman P.S. Attaching a picture. <I would step up the water change frequency... start mixing in RO water... which I would make myself... at home. See WWM re Reverse Osmosis use. Bob Fenner>
Re: phosphate sky high!    5/3/07 Thanks Bob! I have priced RO units and unfortunately being out of work for a few months has sidelined that piece of hardware for a while. Have you used any of the filter media for removing phosphate? <Mmm, not much> Any product come to mind?   <Am actually NOT a fan of such... I prefer water changes, biological... some stop-gap chemical means (e.g. the Kalk trick) for either ab/adsorbing HPO4 or precipitating it...> Seems to be a bunch out there, more inline with my budget at the moment. I was surprised by SeaChem's "no big deal attitude"  when I wrote them about 10ppm Phosphate. <Something is amiss here...> Seems to me any nutrient that far out needs to be addressed. <Agreed> I had no idea when I added the Neutral Regulator it could spike Phosphates that much. There should be some statement on the bottle about its use in planted aquariums. <Or any type> The black hair algae is starting to kill some leaves on my plants. My girlfriend helped me do another water change today, Phosphate is now under 5ppm still a ways to go. <Welcome. Bob Fenner>

Phosphate problems, FW   4/30/07 Dear crew, <Erik> I have recently set-up a 30 gallon tank. I'd like to make it a fully planted freshwater show tank. I have kept saltwater tanks for 20 years but haven't done fresh in a long time. The aquarium has been up for a month with no fish because I am trying to get my phosphate levels down below 1.0 ppm. with no luck. The only things in the tank are 10lbs of Carib sand under 60lbs of Eco-Complete and a piece of driftwood that I bought at a fish store and soaked for a week. <Mmm... this could be the source of the HPO4 here...> Over the month I have changed 100 percent of the water with no change to phosphate. I have tested my tap water and get a reading of 0 for phosphate. The pH is high and I have been buffering that with Seachem's Acid Buffer which claims to not be based on phosphate. I have run Kent's phosphate sponge through my Whisper 40 with no effect and currently have 2 Whisper 40s both with phosphate remover as a last ditch effort. I don't know where this phosphate is coming from as nothing living has ever been in the tank. I have never had the lights on either so no algae is present. Any insights and help is greatly appreciated. Thanks, Erik <I would try two things here... for now... Removing the driftwood (soaking it in more water, testing it there)... and "checking your checker"... testing your test kit against another (possibly at a fish store). Bob Fenner>

Phosphate + pH, FW...   4/30/07 Hey guys, I should have asked this straight out when I asked about my phosphate question, sorry about the dual emails. I mentioned I was lowering my pH with Seachem's Acid Buffer. The problem is that my pH constantly raises no matter how many times I add the buffer. I have a Pinpoint monitor and can see it go up slowly but surely every single time. My pH from the tap is high, around 8.0, but I thought the Acid Buffer would lower it and keep it low. <Mmm... you need to understand the relationship of (the unfortunate term) alkalinity... or buffering capacity... as it relates to pH... You likely have a situation with chemical species that "rebound" the pH... from your source water... perhaps the decor, substrate... Please read here: http://www.wetwebmedia.com/FWSubWebIndex/fwph,alk.htm and the linked files above> But up it goes. Once I add fish and plants I would have to add Acid buffer every single day to keep the pH at 6.8-7.0 as I want it. <You don't want to do this... Such changes should be made gradually... with water adjusted outside the system... not by pouring in chemicals into the main/display tank...> If I went away for a weekend it'd be 7.5 or higher in a day or two without it. Not good for tankmates I'm sure. Any help? I truly appreciate what you folks do for us in the hobby. Erik <Read on my brother, read on. Bob Fenner>

Science Fair Project Dear Mr. Fenner, I am a seventh grade student and I am doing a science fair project for school. The topic I picked to research was the effect phosphates have on green algae growth. I mixed stock solutions of graduated strengths of river water with detergents containing phosphates. I used Cascade detergent and Glass Magic. Glass Magic had more phosphates in it then Cascade. I then added 1ml of green algae to each solution. My hypothesis was that the jars containing river water with the highest concentration of phosphates would grow the most. All of the research I did prior to my experiment pointed in that direction. The actual results were different. The highest concentration of phosphate river water turned the algae to white grains and then it all disappeared. The river water with the next highest concentration of phosphates started to decay and turn brown. This all happened over a three week period of time. I have been searching for books in the library and also on the internet that might help explain my results. I came across a few articles that you wrote and your question and answer segment that you have. You seem to be very knowledgeable when it comes to algae growth. Can you help me. It appears as if the results of my project defy logic. Can you help explain what might have happened to my algae? <Don't know if I can. The "Discussion" of results in a scientific study is often the most important, most revealing part of an investigation. What do you think might be factors, co-factors here? Did you "run controls" with no detergent addition? Perhaps there is/was/were other influences in your test model other than the addition of detergents, phosphates... Is there some reason if the study was about soluble (I take it) phosphate that you utilized dishwashing material? The other chemical properties of these products might well account for the changes you observed... perhaps you might repeat the experiments with just the equivalent concentration of HPO4... Maybe other conditions of light, heat, water chemistry might be tried to see if they'd render the same results, perhaps lower concentrations of the test chemicals would prove less toxic.> I would like to thank you in advance for your time regarding my letter and possible answer to my question. Have a great weekend.                                                                 Thanks,                                                                        Mario <Do consider having a reference librarian show you how to do a computer search bibliography. Please see here re: http://www.wetwebmedia.com/litsrchart.htm Thank you for writing. Bob Fenner>

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