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FAQs on Freshwater Aquarium Circulation

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Best approach for current and O2?      7/20/17
<Hey Jude>
Just wondering what is the best for a 38 gallon tall tank with two angels, 6 Glowlight tetras and one Medusa Pleco.
If I need current for the Pleco what is the best way to obtain that?
<Complete circulation... pulling water from the bottom, to top... and redundancy. Two mechanisms at work at the same time. Perhaps an outside power filter and... Oh, I see you answer the question below!>
I have nothing in there now, but the filter which is an Aquaclear for a 70 gallon. I am thinking of lowering the water a few inches to get splash.
Would that help like an air stone would?
<I would add the airstone here>
Just wondering what is best for the Pleco at the bottom and aeration overall? Thanks
<As stated. Bob Fenner>

Advice on filter/water circulation for 55 gallon  11/13/09
Hello, very comprehensive site, - through the years I found answers to many of my questions here! - Thanks!
<Glad to have been useful.>
There is a snapshot of my set up:
55 gallon
planted with Anacharis, Anubias, Anubias nano, floating Riccia and some duckweed
decorated with driftwood and rocks
2 heaters (temperature at 78-80)
Undergravel filter driven by a small loud pump
One 5 inch plecostomus
One 8 inch Jack Dempsey
One 7 inch Texas Cichlid
One Ropefish (about 14 inches)
<Poor thing! These gentle, gregarious fish are best kept in groups, and certainly away from cichlids and other aggressive fish.>
One Polypterus senegalus - 6.5 inches
<I've seen (Labidochromis) cichlids strip the fins from Bichirs, so to be honest, this the Bichir/Cichlid combination isn't one I recommend.>
Five silver dollars - about 2 inch diameter each
One 8 inch Leporinus fascinates
<Leporinus fasciatus can become extremely aggressive, and is a known fin-biter (apparently natural behaviour). I wouldn't be keeping this with Bichirs or Ropefish, and while I've seen them mixed with cichlids, I've heard of the odd specimen that has become so aggressive it's caused serious mayhem.>
I think I'm barely not overstocking tank or is it overstocked?
<In 55 gallons? Overstocked, and then some. More importantly, the selection of fish isn't at all wise.>
Cichlids compete for space but never gone worse then a lot of shaking at each other and some mild chasing. (prior to this set up i tried a species tank of Jewel Cichlids - that was "Battlefield Laterite" compared to what I got now :) )
<Well, the Bichir is still a baby, as are the Silver Dollars, so I wouldn't get too excited about a "job well done" just yet.>
I used an old Emperor 400 filter with two BioWheels, except it was second-hand and didn't have BioWheels and was very very loud - and finally was taken out of the tank - 4 months ago)
Water changes - at least every 2 weeks change of 5 gallons of water Ammonia is 0, Nitrites 0, i haven't measured PH in a while. Should be pretty hard, since in MN water comes of the limestone, but driftwood should compensate for at least some of it.
<No, driftwood doesn't work this way. Driftwood will lower the pH of soft water by releasing tannic acids; it does not substantially soften water though. For one thing, insufficient surface area.>
No loss of fish since set up of the tank 1 year ago with this exact livestock (they were much smaller, but the y also lived then in a 30 gallon).
<You got lucky. So far.>
4 months after the Emperor Filter was taken out of the tank I noticed slimy dark green clumps growing among the floating Riccia. Looks like green-blue algae to me. Smells nasty - like a swamp (previously tank had only a clean "aquarium" smell - which in larger amounts can be found in very good LFS places).
<Blue green algae.>
Is it a blue-green algae?
Is there is a way to combat it with chemical/biological measures?
<Almost certainly -- as in I'd put $100 down on this -- the problems are two-fold: insufficient water movement, and very high levels of nitrate and phosphate. Blue-green algae is almost a "standard issue problem" with overstocked cichlid tanks, and often a precursor to bigger problems including Hexamita/Hole-in-the-Head, since the conditions that promote blue-green algae are the same ones that reduce the vitality of cichlids.>
Does any fish eat it?
<Not really, no.>
Plecostomus does not - drowned one clump but he showed no interest.
<Plec-type catfish are the biggest con in the game. They are more likely to *cause* an algae problem than fix one. Think about this for a moment. Algae does best in tanks with lots of nitrate and phosphate. Plecs are big, messy animals. Put the two together and you have happy algae. In tanks with big, messy fish algae removal is a two-step process: install bright lighting so that you can add Indian Fern and other algae-busting plants, and then use an algae sponge to remove whatever is left over. That's it. Those are the options. Nerite snails would be great, but the cichlids would likely eat them, but for $ a piece, you might feel they're worth a shot. Do read here:
Also clear parts of water surface are covered with a dimly iridescent film, like spilled grease or gasoline. What could that be?
<If it's golden, then likely Diatoms.>
It does disappear after water change, but comes back within 2-3 feedings.
<Proves my point: it's related to eutrophic conditions in the aquarium.
Hang-on-the-back filters are rubbish in terms of water circulation and I can't recommend them for fish tanks with big fish. I have no idea why they're so popular in America; you hardly see them in Europe, and frankly,
I don't miss them! You need massive water circulation in this tank, I'd say 8 times the volume of the tank in turnover per hour. Adding a big canister filter, ideally through a reverse-flow undergravel, would be the best
solution. Water changes need to be massive. And last but not least, you need to thin out your livestock. For a 55 gallon tank, you have something like three times the number of fish you can keep safely. The "inch per
gallon" rule applies to fish around an inch long, i.e., Neons, Guppies, etc. It OBVIOUSLY doesn't apply to big cichlids and catfish. Think about this for a moment. One Oscar is about 18 inches long when mature, as are twelve Neon tetras laid end to end. Which needs more aquarium space?>
Since largest fish are omnivorous - I feed a mix of bloodworms/mosquito larvae/spinach/peas/algae wafers/occasional feeder or shrimp.
<Why are you using feeder fish? This has been explained endlessly in books and magazines, but let's do it one more time. Feeder fish are "parasite bombs". Any fish bred for a few cents obviously won't be kept in good, hygienic conditions. Furthermore, feeder fish enhance aggression. Most importantly of all, cyprinids (goldfish, minnows, etc) are high in fat and thiaminase, and together these cause MAJOR health problems. Pick up any book on aquarium fish health and it will state in no uncertain terms that feeder fish are extremely bad. Bob Fenner has reported that a majority of non-old-age deaths of Lionfish are caused by goldfish feeders. So there's no real surprise here, and I can't for the life of me think why people still use them. They aren't even sold in England, and haven't been for a good twenty years. While we don't get much right in this country, I think on the feeder fish front we're definitely wise. If you want to offer live foods, choose something known to be safe, such as earthworms.>
Meanwhile fish look healthy and eat/behave as usual.
<For how much longer...? As I say, blue-green algae are common in tanks with poor water flow, limited oxygen, high nitrate, and high phosphate.
That's a cocktail of trouble. As fish grow, they become more demanding in terms of aquarium resources, so the fact they've been healthy when younger doesn't mean they'll stay healthy as they grow older.>
I reasoned that the undergravel filter alone does not serve the tank and I need to shell out for a new filter. This is what I'm looking for:
1. large enough throughput
2. preferred some kind of underwater water output - otherwise may get loud as water evaporates quickly in the summer.
3. quiet (tank is in the living room of a co-op and my mates will fry my cichlids if I raise DB level of the house again :) )
4. under $100 of at least under $150
<Since I'm not in the US I can't really price things up for you. But I'd mention that a Classic Eheim 2217 costs around 27 UK Pounds and has a turnover of over 250 gallons/hour. A couple of those would really help.
They're built to last and very quiet. So while pricey, Eheim filters are by far the best value since they routinely run for over ten years without problems. There are plenty of cheaper options, and a budget external canister plugged into a reverse-flow undergravel shouldn't break the bank.>
What would be your recommendations?
<See above. Alternatively, take back a bunch of fish, and keep two or three fish suited to this tank, maybe the JD, the Texas, and the Plec (but anything with the Plec is going to be filthy). Personally, I'd have stuck
with the Bichir, three Ropefish, and maybe a school of Congo Tetras or Rainbowfish for the midwater. I'd still have space for a Bristlenose Plec, which is smaller, cleaner, and does remove some algae.>
what else can improve water quality of the tank?
<Many, many things.>
Huge Thanks for help! - Elena
<Hope this helps. Cheers, Neale.>

Re: <sic> advise on filter/water circulation for 55 gallon  11/13/09
Thanks for the answer!
<You're welcome.>
I'll work on thinning the tank - frankly I knew long ago it's far from the best mix, but as it happens Cichlids' antics grow on you.
<Yes indeed. But they *are* demanding fish in so many ways.>
Bichir was the first fish in this set up - bought him 3 years ago at a size of a matchstick, and I'm bent on keeping him while getting better tank mates.
1. Trade in JD and Texas cichlids, potentially trade in the Leporinus (I've seen aggressive behavior from some in the stores and while mine is peaceful, it could be just the cichlid presence that makes him so)
<Likely depends on the fish, the environment, and indeed as you say, the companions.>
3. if possible get more ropefishes - 1 or 2 more, It's all i can afford at the moment.
<Maybe swap the cichlids for them? Trust me: get three, and a nice hollow ornament, even a halved flowerpot, they can hide in, and you'll be charmed by them. They enjoy hanging about in groups, all tangled up, with their heads poking out of their cave.>
4. I'd like to may be get a few smaller cichlids that would display personality and add to the tank?
<Pelvicachromis spp. work great with Bichirs and Ropefish, as would anything reasonably small and mellow, e.g., Keyholes, Flag Acara, maybe even Blue Acara or a Firemouth (these are aggressive when breeding, but otherwise easy-going).>
For all my love to Polypteridae - they are not as colorful and fun to watch as cichlids.
<Understandable. Congo Tetras and Leopard Bushfish (Ctenopoma acutirostre) are my favourites to fill this niche. Bushfish are easy to feed on wet-frozen bloodworms and other such treats, and don't need feeder fish, despite what some might suggest. Congo tetras and Bushfish are from Africa, so together with the Bichirs and Ropefish, you have a nice African scene.
Add some Anubias and floating Indian fern for shade, and maybe a school of Dwarf Synodontis on the catfish front... what more can you ask for?>
I think of a couple Convicts, may be a Kribensis (couple),
<Convicts wouldn't be more choice at all; Kribs, and indeed other Pelvicachromis spp., like Pelvicachromis taeniatus, would be fine choices.
Since you're in MN, you might get in touch with one of the fish clubs there. I happen to be talking to one of them in Minneapolis in January, so know of at least one. Fish clubs are a great way to swap unwanted fish, to obtain plants and fish cheaply, and to track down "rare" fish you don't see in pet shops. But having said that, all the fish I've mentioned so far are in the trade and easy to order, even if they're not in the tanks this very day.>
Please advise!
Thanks Again! - Elena
<Cheers, Neale.>

Re: <sic> advise on filter/water circulation for 55 gallon  11/14/09
this will be the last email from me - I got more then enough info already!
what about a Black Ghost Knife as a Bichir/Ropefishes companion in 55 g - MonsterFishkeeper forum recommended them as suitable tank mates for bichirs (and they are probably most beautiful fish ever!) - may this work or is 55 gallon too small for BGK?
<In terms of temperament, yes, non-aggressive Bichir species can cohabit with Black Ghost Knifefish. HOWEVER, do understand that Apteronotus albifrons is one of the most delicate fish commonly traded, and most specimens (surely 90% of them) die within a year. Given these fish can live 20 years and get to 45 cm or so in length, that's a sign folks don't keep 'em well. They are extremely sensitive to "old" water with high nitrate levels. They come from shallow, fast water habitats around rapids and waterfalls, so expect lots and lots of oxygen and water current. While your Bichirs would be fine with that provided the tank wasn't too deep (Bichirs are air breathers, so have to be able to swim to the surface) if you are having problems with blue-green algae, then it's likely your current filtration system is far inadequate for a Black Ghost. Oh, and it should go without saying that apart from inoffensive dwarf cichlids, you can't reliably mix cichlids with Black Ghosts. Sure, some folks do, but as/when they keep 'em alive for twenty years, then I'll accept it's do-able. For the most part, cichlids are poor tankmates for Black Ghosts. Too much competition for living space and food, and high nitrate levels are even more lethal to Apteronotus than they are to cichlids. Exceptions might be made for cichlids from similar fast-water habitats, e.g., Steatocranus and Nanochromis, but these are difficult fish to keep at the best of times, and not viable in the average community tank. Well oxygenated, fast-flowing, somewhat cool (24-25 C) water will be needed.>
If you know any clubs in Minneapolis I'd appreciate a contact info. I'm still new to the city and only know of World of Fish store (may be you know of them - largest in the city) and Aqualand (also a reputable store, bought my Ropefish there and got a deal on 10 gallon tank for crustaceans) - but not of any clubs!
<Well, the one I'm visiting is the Minnesota Aquarium Society in Roseville, MN, apparently not far from  Minneapolis.
There may well be others.>
Thanks - Elena
<Cheers, Neale.>

Water Movement  10/30/08 Hello Crew, <Hey - Mike here today, having (mostly) recovered from Hurricane Ike> Certainly hope things are going well for you there. <Getting there...> Starting to get a little cold here in Florida which is a good break from all the 90+ degree days. <It's nice and cool here, too - finally!> I am setting up a 75 gallon fw tank and have been debating over what kind of filter to use. I just found out my neighbor has 2 almost new hagen Aquaclear 110 filters that he doesn't plan on using, and he is giving them to me for nothing, so I am going to go with both of those on the tank. However, I am using a sand bottom with no live plants and I know vertical water flow is necessary to bring the detritus off the bottom to get in the water column. Please tell me what you would recommend for this. I need something that will move the detritus but not stir up the sand. Also, do you know of any type of sponge pre-filter that would fit over the intakes of the AquaClear filters to keep sand from getting into those. Thank you for your help and all you do, and have a blessed day! <The 110's should provide plenty of water movement and filtration, and should be all you'll need (as long as they have their ceramic bio-media). Small overflow sponge pre-filters should work as intake screens, and are available off the web. Good luck with your new tank! Setting up a 175 this weekend...new baby Mappa puffer :)> James Hall <M. Maddox>

Questions (water circulation), FW 10/23/08
Hello, hope your day has been going well so far!
<Tis, thank you.>
Before I ask my question I want you to know that I truly did try to find the answer on your website. If it was there I missed it and sorry. I am going to have a 75 gallon fw fish only tank with no live plants. I will be using power filters and no canister so I know I will need water circulation. Please tell me if utilizing 2 powerheads are a good choice, and if so, what output size and where the best placement would be.
<The power filter alone will provide the flow you need assuming it turns the tank over at least 4-5 times an hour.>
Thank you for all your help.
<Welcome, Scott V.>

Re: Questions (water circulation)   10/23/08
Thank you. I will be using sand as a substrate. So the filter should provide enough circulation to remove the detritus from the bottom and put it into the water for removal?
<That's certainly the theory. The more circulation, the less likely dirt will collect on the sand. If you keep one corner of sand "lower" than the rest, the dirt will collect there, and it is the easiest thing in the world to use a turkey baster to pipette out the dirt when it becomes annoying. Dirt sinks into gravel, but it floats on top of sand, so while sand may LOOK like it gets dirtier faster, it's actually much cleaner because the dirt isn't hidden away in the gravel. I find maintaining tanks with sandy substrates really easy, and all my tanks have them. Gravel is SO twentieth century fishkeeping!>
Thanks again.
<Cheers, Neale.>

Surface splash vs. water movement   2/6/08 Neale, I hope you get this one. You've been so helpful to me and so many others. I'll try to make it as short as possible. <Hello again Mitzi!> I'm putting my Oscar (and a young common Plec) into an 8' long 250 gal tank and am crossed-eyed reading about filtering options and surface agitation. I still haven't found a definitive answer. I've always used HOB filters and don't want to mess with sumps or drilling. <Indeed.> The important question I have is this....do I need actual surface agitation if I've got more than adequate *water turnover*? <The latter is more important than the former, though more specifically what you want (especially with catfish) is a filter that effectively draws water from the bottom of the tank and sloshes it out at the top of the tank. In other words, circulation. If the filter inlet is only halfway down the depth of the tank (as is often the case with smaller filters) then the bottom layer of water might hardly move at all. Thing of the surface area at the top as the "lungs" and the water in the tank as the "blood"; the job of the filter pump is to be the "heart", pulling all the water through the top if the tank periodically so it can be re-vitalised with more oxygen and get rid of any CO2.. I'm going to use external canister filters (pond filters maybe) that will give me 10-13 times the turnover rate per hour with no airstones. <Should be ample, especially if the inlet and outlet are pipes are placed strategically around the tank to maximise circulation.> Do I need something that actually splashes the water's surface like a hang on back filter does? <The splashing is a nice thing to have because it "folds" the surface area, effectively increasing it (to go back to our pulmonary metaphor, rather like the alveoli in your lungs). But is it essential? No.> Or is water movement equivalent to surface agitation? <Water movement, provided it is circulating the water in the whole tank, is better.> Thank you so much for your time. Sometimes the simplest things aren't quite so simple when you think too hard about them. Mitzi <Ah, but sometimes if you think about them in simple terms, they become simple again. Water circulation, like filtration, can be made overly complicated when you worry about whether this system or that system is better. When you actually come right down to it, the basic principle is very simple, and so is the solution. Cheers, Neale.>

Re: Surface splash vs. water movement   2/6/08 That makes me feel better about the whole thing. My goal was to have no dead spots. I want to put two 900 gph pumps attached to canister filters at the ends plus a couple magnetic 1050 gph powerheads. If I can just use U-shaped return hoses hung every 2 feet on the back of the tank, I can put the ends of the hoses at the top of the water level. It'll move the water a little when it goes it but it won't be a big splash like the HOB filters. The LFS owner said to use powerheads that shoot air into the water, but I want my powerheads towards the bottom (like your idea) so it pushes the bottom water towards the filters. The LFS said "just drill it and use a sump" but I don't want to mess with plumbing and don't want to have the tank drilled. I just wanted it to be as simple as possible. Do you think it will work the way I want to do it? <Probably.> I'm in his tank every day vacuuming his sand, it drives me nuts having "fish poo" on the bottom. I'm hoping lots of water movement will shove it all right into the canister filter :-) The LFS said it's "over-filtering" for 2 fish but I don't think that's possible with an Oscar and a Plec. <Indeed.> I just don't want the fish to be shoved around the tank. Do you think it'll be too much water movement? <The Plec will certainly be fine, since they're adapted to rivers, and can suck themselves onto things if they feel overwhelmed. Many of the Loricariidae (though not the common Plecs) are rheophilic in the wild, i.e., they actually prefer rapids over other parts of the river. As for the Oscar, this depends on the fish and how turbulent the water is. What Oscars don't want to is lots of churning water. But a good steady flow, with perhaps one or two gentle spots behind big rocks or bits of wood, should be fine. I wouldn't go over 8 or 10 times the volume of the tank in turnover though, at least, not initially. It takes a while for fish to get themselves used to stronger water current if they've been in sluggish water beforehand.> Thank you! Mitzi <Cheers, Neale.>

Re: Surface splash vs. water movement -02/06/08 Thanks, Neale. I may start out with slower pumps and see how it goes. He's got an 850 gph and 4 Emperor 400 Bio-wheels on his 6' tank now and does fine with them. Plays in the powerhead all the time like Loaches do-hilarious. Thank you for answering the "splash vs. water movement' question for me! That was my main concern. Mitzi <Cool. Good luck with the home improvements! Neale.>

Overflows and return pumps, FW...    8/8/07 Hello Crew! <Danny> I have an 86 gallon FW heavily planted tank with a 20 gallon sump (still under construction, the sump not the tank), and an external, HOB overflow box. I am using an Eheim 1261 return pump with 3/4'' plumbing to the tank, and I mistakenly used 1" drain plumbing from the overflow to the sump. The pump, needless to say, overwhelms my overflow. To rectify this, I was thinking of adding a ball valve to the return to throttle back the return pump. <Mmm, perhaps better to divert this excess flow back to/through the sump... via a Tee and a valve...> But, I want to upgrade the drain. Should I go with 1-1/4" drain or 1-1/2" drain? <The bigger the better... for flow, as well as noise reduction. But... better still would/will be to add yet another overflow box if going that route> I don't really want to throttle back the pump, if I don't have to. I want to avoid overrunning the overflow at all costs. The overflow has a 1-1/4" bulkhead, but it also has a 1" pipe for holding the pre-filter. It seems that no matter what size drain I use, the 1" pipe is going to be my bottle neck. <Yes> I have heard of drilling holes in the 1" pipe to alleviate the bottleneck there, but I think it will introduce a lot of noise. Any suggestions? Is there any downside to restricting the return pump (aside from the obvious loss of gph?)? Thanks, Danny <Please read here: http://www.wetwebmedia.com/marsetupindex2.htm the yellow tray... re plumbing... The same input applies here to all tank types. Cheers, Bob Fenner>

Question about sand and filter impellers -- 06/11/07 Hello everyone, <Hello.> I have a question about sand's effect on hang-on filters. I added some extremely, extremely fine sand to my tank (it's by Zoo-Med, called "Repti-sand"). It's made of quartz and is very, very fine and light, so much that it took about 2 days until the water was clear after I added it to the existing tank. Really, it's more like dust than sand. Anyway, I have four emerald Cory's in there now, and they love scooting around in it and it's very soft so it's easy on their bodies. It also hasn't affected my pH. I've had it like that for about a week and a half, and then last night the filter started making some grinding noises, so I pulled it out, rinsed it out (some sand came out) and tried to get it to work a few times. Then I looked online and read about impellers, and I saw that the impeller was broken (its blades go around and around). Do you think it's the sand that caused it, or my jiggling it around and taking it apart a few times trying to get it to work, perhaps not being gentle enough, that did it? That one was a Penguin Bio-wheel, and I got a new one today, an Aqua Clear with the different style of filtration. This one's making kind of a gritty noise as well, and I'm afraid it will break, too. Is this a common problem? Do you think I should get rid of the sand, or at least get some heavier sand that isn't so easily disturbed and sucked up into the filter? I do want to keep some sort of sand because I want to get Kuhli loaches later on. <Sand can damage the impellers of pumps. It isn't common though. I use silica sand in all my aquaria, and while sand sometimes gets stuck inside the filter canister, it doesn't seem to do any harm. But your own mileage may vary! Silica sand in particular is quite heavy and settles very quickly. The only time it gets into the water column (and thus into the filter) is when a big catfish decides to swish into the sand and dig herself a burrow. Small things, like Corydoras, simply don't push the sand far enough off the substrate to cause problems. Now, if sand gets inside the impeller, it can quite possibly cause some rattling noise. In the long term, anything that clogs filter media forces the impeller to work harder, and puts all its components under more stress. You probably want to make sure the filter inlet is far enough above the substrate that the fish can't swoosh the sand into the filter. Adding a decent pre-filter layer to your filter system (such as filter floss) is also a good idea. My gut feeling is that while silica sand has been used for many years by many aquarists without problems, finer sands like your Repti-sand might be just a bit too fine for safe use.> Thanks for any and all help you can offer! I really appreciate it! Allison Evans <Hope this helps. I'm a BIG fan of sand in aquaria, and agree with you that loaches and catfish really benefit from its use. But it does need to be handled properly. Cheers, Neale>

pH and water flow  5/17/07 Crew, <<Hi, Erik. Tom with you.>> Great site, thank-you. <<Thanks, Erik. Glad to hear we've been helpful so far.>> I have a 30 gallon tank with Eco-Complete as substrate and nothing else in it. I use RO/DI water. My Pinpoint pH monitor reads the pH as 7.2 and up with the Whisper 40 running (only has carbon in it) and reads 6.75 and lower with the filter off and not flowing at all. Why? <<Well, now both of us have an issue to deal with. Your issue is that pH monitors don't work well in purified (RO/DI) water. Mine is trying to explain, in simple (?) terms, why they don't. First, and not surprisingly, RO/DI water has very little in the way of buffering capacity which means that pH can change quite readily, up or down. Simple enough. Second, commonly our pH is affected by the absorption of CO2 from the atmosphere. This is why you can expect pH to typically decrease over time since dissolved CO2 in the tank lowers pH. How quickly this takes place depends on a wide number of factors but, once again, this can depend, in part, on the buffering capacity of the water. In our homes, CO2 levels can be, and typically are, higher than outdoors yielding a higher concentration of the compound in the air and, therefore, greater opportunity for our tanks to absorb it. (RO/DI water generally runs in the pH range of about 5-7 depending substantially on the level of dissolved CO2.) Third, CO2 is 'driven' out of the water by agitation such as what you might create with airstones, UGF's, HOB filters, etc. Though this doesn't even scratch the surface of a highly complex topic, I believe that what you're seeing is the absorption/dissolution of CO2 in your tank caused by calm periods (filter off) resulting in increased CO2 absorption (lower pH) followed by active periods (filter on) resulting in decreased CO2 (higher pH).>> Also, the readings on the pinpoint monitor fluctuate a tenth of a point constantly, it is never pegged. I know constant pH is better than a specific reading and I can't get the pH to stay at one reading even in this small tank. <<The greater the precision of the instrument, the more likely it will be to show variances, Erik. You might think of it like the 'refresh rate' of your computer monitor. The higher the refresh rate, the more screen 'flicker' you'll observe. Your Pinpoint monitor is constantly refreshing its readings. In conjunction with what I've already discussed, I'd be very surprised if it weren't constantly fluctuating. A very nice piece of gear but it has drawbacks in this particular set of circumstances.>> Respectfully, Erik <<Hopefully this will shed a little light on your situation, Erik. Best regards. Tom>>

Automatic leak detector/ water valve shutoff system?    5/2/06 Hi,      I have a FW African 120G plexi tank that is plumbed through the bottom through a double size Lifegard set (UV, mech, chem, and heater modules) then back up through spray bar towers in the corners, the tank is visible on three sides so it was important for me to have as little filtration/equipment in the way as possible. I have three drains that T into one 1" pvc line, and the strainers are only perhaps 1.5 inches above the sand. Looks great, works great, but what if there is a leak!?!? <... water on the floor, possibly drained down to their level> It has been up over 6 months or so and have had little trouble, but it is always in the back of my mind. Ideally I would rig a leak detector up to a relay that upon detection of leak, it closes the in/out ball valves and turns off the UV and pump. <There are such alarm devices on the market>       I have the leak detector circuit and am fairly competent on wiring all the relays, but what is holding me back are the solenoid valves. <Where would you install these that would help?> I thought that I would be able to use a sprinkler valve as they are cheap and pvc, but to throw the ol monkey wrench in my plans, it has to have a minimum of 15psi to operate correctly. I am running 3-5 tops. Does anyone know of a different type of valve that would fit the bill? <None that I would use> I know I can put a check valve on the return line, which I should have done in the first place, but I still would like at least one that would close the system down if I were to spring a leak.      In the meantime I have plans to raise the drains up so if it does happen, at least my fish may have enough water to survive the event, and also I think I may drill a drain through the floor (under the tank in the cabinet) as to not flood my room. Any advice? thanks! <Mmm, I would not worry here. The likelihood of a disaster is likely very small... Next time/tank, either drill through the back or run the (return) lines over the top, the drains through the tower/s. Bob Fenner>

Too much filtering or water movement How much is too much? - 20/1/05 I was wondering what would be considered too much water movement. I have a 75 gallon tank and one Fluval 405. I wanted to put in a second Fluval 405 to make sure the tank stays nice and clean. But then I was worried about the problem of too much water movement. Right now the fish in the tank don't seem to have any problems with the one filter. What do you think? <Depends on the fish (and, more importantly, corals. However, in general, fish can withstand - and sometimes prefer - far higher currents than we provide. Ever swum in the ocean? Or a fast flowing river? If I am right in thinking that a 405 provides a max. flow of around 350gph, then two such filters would be perfectly suited for freshwater.... I would be looking for more flow for most marine tanks. Best regards, John> Rusty

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