By Bob Goemans
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Bob Goemans corresponds with Cesar Silverio

Cesar Silverio writes...

Hello Bob,

Here I am again disturbing you with my tank problems, but I can't find in Portugal someone I trust to help me solving these questions. So after nine months since our previous e-mails (attached) I am going in this e-mail do make an update of my tank problems and I ask once more for your help to solve some remaining (and serious) problems.

Concerning nitrate and phosphate problems with the salt mix, I am still using the Tropic Marin Pro-Reef Salt and the test analysis is now usually zero for both compounds (No3/No4 and PO4). I suppose the high values I referred in my previous e-mail were an occasional situation.

I followed your advice and bought a Nitratereductor from Acquamedic and my nitrate problems became solved; usually my nitrate readings are now between 5 and 10mg/l, but I am not using it at the moment , because after reducing nitrates the device started to consume sulfates and it smelled like rotten eggs; according to manufactory instructions, I increased the flow rate and the previous stinky smell faded but different one came out and I had to turn off the nitrareductor .

My main problem at the moment are phosphates levels and once again I ask your help to help me solving them.

After months of starving fish and corals, killing a few SPS and using continuously Rowa phosphate remover in a canister filter with no success reducing phosphate levels ( the results of my electronic test never came below 0,40 m/l), I realized that the phosphate source should be inside the aquarium (sometimes I am a bit slow...) and took the decision of asking for a definitive solution: My first decision was to remove the Miracle Mud from my refugium. A few days later PO4 values still remained at 0,60 mg/l, showing that the problem was still there.

Then I thought the problem came from the plenum, but before remove it, I decided to remove some sand from the plenum mix it with a small quantity of new saltwater (PO4 =O mg/l), let it rest 2 days in a plastic bottle and test it for phosphates; the test result was 0.14 mg/l (at this moment the aquarium levels for PO4 were 0,45 mg/l), so once again I have concluded that the problem was not in the plenum sand (do you agree on this?)

Then I decided to use exactly the same method to test tank bottom sand and I suppose I found here the terrible diagnosis for the problem: PO4 = 0,65 mg/l.

Please let me know your comments on this (do you agree with my conclusions?) and please help me in order to solve this problem giving me some advice about it.

Is there anything I can do to remove phosphates from the aquarium sand bottom without removing the sand? I suppose I know the answer for this question but I can't face it.

Do you have any suggestions how to remove the sand with minimal disturbance for corals?

I am not using at the moment kalkwasser or any other additive to boost alkalinity. My calcium reactor alone provides calcium and alkalinities levels enough (Ca = 450/480 mg/l, KH =10/11dHK) for the moment (corals, due phosphate problems are not growing); do you think after solving current phosphate problem I should/need to install in my tank a kalsswasser reactor in order to help the fight against phosphates, or do you think if I do that it will result in too high levels of calcium, alkalinity and pH?

Regards Bob and once again thank you for your great help

Cesar Silverio

Lisbon, Portugal

Bob replies...

Hi Cesar,

Quickly, tell me what you're feeding as of now, how often, and if any additives are added. (Are they different than what was in your previous letter?) Also, do you test the water used for water changes and evaporation make up? What brand RO/DI are you using? What brand PO4 kit are you using? Bob

Cesar Silverio writes...

Hello Bob,

Thanks you for your help. For the last 2 or 3 months now, I reduce a lot the quantities and stopped the frozen food for fishes; Now every morning I give 1 sheet of dry algae and at night (5 times a week) 4 or 5 ml of varied dry food (granules) and a pinch of Cyclop Eeze; I am not feeding frozen foods for fishes at the moment; for corals I give once a week using a pipette 3 half cubes (6 grams) of a varied frozen foods and once a week 5 ml of Salifert Coral Food. I stopped adding additives (Sr,I,Trace) two months ago.

The water coming from RO/DI (Maxima RO/DI) before and after Red Sea Coral Pro is free of phosphates. For testing PO4, I am using an electronic photometer (Martini Low Range Phosphate Photometer- Milwalkee Instruments).

Thank you once again


Bob replies...

Hi Cesar,

Thanks for the fast return. Lets look at the ways phosphate can enter the water with first looking at one of your concerns, that of it possibly coming from the substrate, either that of the mud bed in the refugium or that of the plenum's bed.

To begin, it's been said anaerobic areas, where obligate anaerobic heterotrophs reside, accumulate phosphate. Actually, the word 'accumulate' is somewhat incorrect. Yes these bacteria are inefficient and produce copious amounts of phosphate. However, the anaerobic area with its lower pH and redox is a fairly efficient user of the oxygen electrons 'tied' to the phosphorous element. This results in the phosphate being reduced back to phosphorus. That's a good point for deep beds, (but the only one that I can think of) as most of its substrate is in a truly 'anaerobic' condition. It could also then be said phosphate accumulates anywhere its not attacked for its oxygen elements. That would tend to say that in the more 'aerobic/anoxic' zones there would be greater accumulation, however, that's also not 100% accurate! In those areas it's mostly bound to calcium where it's quite stable because it's very easy in those areas to maintain its 'charge' balance because of the surrounding diffusion of oxygen. Therefore, phosphate is usually not available for uptake in substrates unless directly associated with reducing conditions/covered by bacteria films/mats.

However, if we take this one-step further, where there is infauna, they depend on getting dissolved oxygen to live and have to link with the substrate surface, whereas the bacterium described above do not. This opens the door to the irrigation/tunneling processes of infauna, (or disturbances by other larger animals or the aquarist) which can bring phosphate to the bed surface; however, even though feasible it's probably a rare happening. Nevertheless, it's a possibility and when and if it occurs, it's in the form of orthophosphate, something not registered on aquarium phosphate test kits and which can easily cause algae blooms. Keep in mind infauna also ingest sources of phosphate and produce phosphate-laden wastes. Nevertheless, they are more movers of the compound than users. Therefore, to think the sediment was to blame for you excessive PO4 levels is incorrect.

Since the tap water is purified and tested before use in the aquarium, it appears that it also cannot be the cause of this excess PO4 situation. A poor grade of activated carbon can add to the phosphate problem, and that's worth checking by placing some in a jar of pure water and aerating for a day or two. Then testing for PO4. Lets say that is also not the problem. Since you use a quality protein skimmer, that should help somewhat alleviate this situation, as a good skimmer helps reduce PO4, yet not eliminate it. Nevertheless, would recommend going to a larger Deltec unit, possibly the AP701 or AP851 as you still feed heavily. We have also investigated the salt being used, and we both agree that Tropic Marin is phosphate and nitrate free - and I am now trying that brand and fully agree. So the salt mix has now been eliminated. And we looked at the brand test kit/device being used, and agree its one of the best.

Of course, one of the best ways to greatly reduce PO4 is with a product like or similar to ROWAphos and which is properly used in a phosphate reactor or in a canister filter. And as previously mentioned, its media replaced as soon as there is a visible reading on the test kit/monitor. This is something I do with my systems, and it proves to be a very successful way of controlling this compound, which will, even with all the aspects mentioned above properly cared for, still be an item to control because of the food entering the system.

Well, with all of the above said, that only leaves one way for PO4 to enter and that is with the food entering the aquarium. Possibly, that's a subject that is difficult to rectify because all aquarists are concerned about their animals getting the proper types and amounts needed to maintain them in a healthy fashion. But, ...since we have nowhere else to go on this issue, let's take a look at your feeding regiment

I've gone back to your livestock list, both inverts and fishes and have the following comments - when it comes to dispensing foods onto corals, especially liquid foods, its my opinion they mostly go to waste! Probably 90% goes into the surrounding water and eventually greatly adds to the phosphate level! I personally 'never' use such type products in a large aquarium where overall water quality issues affect other species in the tank. Nevertheless, various brand phytoplankton and/or zooplankton products are used in small systems where their filtration is beefed up/highly increased to handle the increased biological needs. In large systems, I do not directly feed soft corals, but do feed some types of stony corals with Dainichi Marine Reef Veggie FX, which contains Cyclop-eeze. I simply put some of these tiny quick sinking pellets into a small plastic vial, fill it with aquarium water, then make sure all pellets have sunk in the tube, shut the water flow off in the aquarium, then quickly sprinkle them on my Brain Corals, Acans, Micros, Dendos, etc, who gobble them up! I do this quickly because they begin to stick to each when wet. Sinking shrimp pellets are also used on some of these corals from time to time, or directly fed other tasty foods, such as tiny pieces of shrimp flesh. I'm very stingy when it comes to feeding these corals, as its done only every few days or more, and no food is wasted. As to feeding fishes such as you have, large tang, butterflyfish, pigmy angel, etc., you would see them eating this food also, as I've seen it fed in shops to similar species and they gobbled it down while the pellets sank through the water or from the bottom area. This is not to say this is the only food that should be fed, but it is easy to feed, both to corals and fish, and can be done in a non-wasteful manner.

As to a full sheet of Nori per day, I think that adds greatly to the phosphate level, and that amount is unnecessary for those in your aquarium. My preference would be a single strip, about 2 cm wide on a lettuce clip every other day. As said, I've found this alga to increase PO4 levels in previous aquariums when uneaten amounts lingered throughout the day in the system. Even though a very good product, and that some fishes are like cows and take small amounts throughout the day, quantities deteriorating in the water 'do' negatively affect water quality. I know some aquarists feel good by providing their herbivores something to browse on throughout the day, yet that quantity needs to be 'adjusted' so as not to affect water quality unless they have 'extra' large filtration systems. Preferably, feed small amounts several times a day if feasible. Again, PO4 in your system is mainly coming from the foods entering the system.

In closing, since there is apparently no other avenue open for PO4 to come into your aquarium, I suggest rethinking the feeding types and amounts currently used. Also, consider increasing the size of your skimmer and the 'amount' of PO4 removing media used, how it's used, and how often it's changed.

Hopefully, you find this helpful.




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