Flow rates for a large fish tank   6/22/11
Hi there
I really appreciate the assistance and help you all provide as you have done in the past for me.
Anyway, after spending time reading articles on your site I had a few questions concerning flow rates for a large freshwater tank.
I have a custom 300gallon acrylic tank made of 3/4" body with dimensions of 96"wide x 30"deep x 24" high. I want to make a Malawian cichlid tank with Haplochromis and peacock species. I want to get about 3000 gallons/hour to achieve the 10X turnover rate as recommended. I have two overflows with each one having 1.5" and 1" lines. I have an 80 gallon wet dry filter and wanted to know if it is okay to drain 3000 gallons into the wet dry sump by enlarging the 1" bulkheads to 1.5" so I have four 1.5" drains feeding into the wet dry filter. I would then have a larger return pump feeding 3000 gallons/hour back to the tank over the back in a closed loop system along the top perimeter of the tank. Is there any benefit to double the flow rate through a wet dry filter to make the 10X flow rate if the filter can handle this extra capacity? I would have to drill and add two more 1.5" bulkheads to the top of the wet dry sump over the filter pad.
Another option would be to only drain 1500 gallons/hour through the two 1.5" bulkheads and returning this with a pump back through the existing 1" lines and having another 1500 gallons/hour going through a closed loop system over the back and along the top perimeter of the tank. I would then have two 1500gallon/hour pumps at the proper head height to make the 3000gallons/hour 10X flow rate. Of those two options, what would be the best option? Any other advice is also appreciated.
I also have a 125gallon All-Glass tank with overflows that I want to use as a Central American cichlid tank and wanted to apply the same approach for filtration and flow rate as the 300 gallon tank.
Thanks for the advice.
Steve
<Hello Steve. Malawian fish generally want a high flow rate, so anything between 8-10 times the volume of the tank will be ideal. I wouldn't go substantially above this level unless I was keeping very large fish or species particularly adapted to surf conditions. The way you do this doesn't matter hugely, but if you can spread out the current so there is movement at the bottom as well as the top, so much the better. Marine-style aquarium filters are very good when used with Malawians, so any of the options involving a sump and a filter outside the tank has much to commend it, especially if you can place some bags of crushed coral in the sump to provide extra buffering against pH drops. Because plants aren't a major feature of Malawian tanks, the fact the overflow and sump drive off CO2 doesn't matter. In short, choose whatever method of filtration works for you in terms of budget and maintenance. Likewise, what works for Malawians is broadly applicable to Central Americans, except that water chemistry needn't be so hard. Do be sure to read Mary Bailey's article on Peacock cichlids, here:
http://www.wetwebmedia.com/FWsubwebindex/MalawiPeacocksAulonocaraMaryB.htm
Cheers, Neale.>
Re: Flow rates for a large fish tank  6/23/11
Hi Neale
Thanks for the previous information
I was also curious about what your advice would be about the two return options about the wet dry setup with the bulkheads I mentioned earlier as seen in my previous post below. If you could provide recommendations that would be great.
Thanks
Steve
<Hi Steve. I have no opinion either way! Would suggest you read this article re: bulkheads as written for the marine side of the hobby; the basic concepts hold true in a Malawian system where water quality and flow rate characteristics are very similar.
http://www.wetwebmedia.com/BulkheadFloRateArt.htm
Do also read the articles Bob has penned on marine aquarium plumbing generally:
http://www.wetwebmedia.com/plumbingmarart.htm
In broad terms, most overflow and sump systems work well, but certain designs, flow patterns work better than others. Cheers, Neale.>

Powerhead Position 6/3/11
Hello WWM Crew. My name is Eldrich Freeman and I need your help.
<<Nice to meet you Eldrich, I'm Adam and we will do our best to assist you tonight.>>
I'm not sure if you've answered this question or not. I'm new to this site so I wouldn't know where to begin as far as searching for the answer...
<<Next time I would start here;
http://www.wetwebmedia.com/wwmadminsubwebindex/question_page.htm
There are recommendations on how and when to submit a query as well as our Google search function, which could lead you to great articles and FAQ's on your very subject like these;
http://www.wetwebmedia.com/circmarart.htm 
http://www.wetwebmedia.com/powerhdfaqs.htm.
...when you're done with those articles the Google search function for the site is also at the bottom of them as well.>>
My problem is figuring out where to put my power heads. I have 2 Marineland Maxi-Jet 1200. As power heads they're doing 295 gph. I have two Rena Filstar Xp3 canister filters.
<<I prefer in general (very general terms really without knowing more about what you keep) to have turbulent flow vs. linear flow, as in traditionally shaped/sized tanks it creates less dead spots. You can achieve this by placing the power heads next to each other with the outlets positioned so that the streams cross (Ghostbusters say not to cross the streams...but it's okay here) or you can place them opposite each other in the aquarium for a similar effect as well.>>
I have a 135 gallon (long) aquarium. My question is where should I put the power heads and do I have enough for proper circulation?
<<This depends on what you plan to keep, I didn't see any indication as to what type of animals you will be caring for in this query.>>
Do I need to add something else to the tank.
<<See my last comment again, if you give me some details about your livestock or planned livestock, I'd be glad to help. Depending on what you want to keep, you may or may not have the necessary equipment, so that's why I need to know that. Assuming you want assistance in that regard as well>>
The dimensions for this tank is 72x18x25. I really need your help. I want to provide the best home for my fish. Thanks for your time.
<<Anytime, good luck. - Adam J.>>
Re: Powerhead Position 6/4/2011
Hello WWM Crew. This is Eldrich again. I have a 135 gallon aquarium and I trying to figure out the best circulations for the tank. I'm planning to house about 15 - 20 African Cichlids (Mbuna)'¦
<Do plan this carefully'¦
http://www.wetwebmedia.com/ca/volume_5/volume_5_2/malawian_cichlids.htm
http://www.wetwebmedia.com/fwsubwebindex/DwarfMbunaArtMaryB.htm
Mbuna are notoriously difficult to do "right" -- and if you get things wrong, you end up with psychotic fish, dead fish, hybrid fish, and a tank that looks like a bunch of junk.>
I'm also going to incorporate cichlid stones and sand banks for the tank. I have sand as well.
<Now, again, do think carefully about what you're doing. Some Malawian cichlids do need sand, and some need open water:
http://www.wetwebmedia.com/ca/volume_6/volume_6_1/placidochromis.htm
http://www.wetwebmedia.com/FWsubwebindex/MalawiPeacocksAulonocaraMaryB.htm
Neither Placidochromis nor Aulonocara are groups of cichlids that will work well with Mbuna, which are cichlids that need rock. So decide on what it is you want to keep, and optimise the tank accordingly.>
I was also thinking of putting Texas holey rock in the tank. My question is do I have enough for proper circulation? I have a 2 Marineland Maxi-Jet 1200 that pumps 295 gph as power heads. They also convert to 1300 gph circulation pumps. I'm not or I don't want to use air stones of any kind. I don't want to have any dead spots. Will this be possible with the equipment that I have?
<You're after 8-10 times the volume of the tank in turnover, so yes, for a 135-gallon tank, about 1300 gallons/hour is about right. Of course you'd want most of that to be filtration, so I'd tend to concentrate on that side of things, and then just put one or two powerheads in strategic corners of the tank where a bit of extra push is needed to stop solid waste building up.>
The dimensions for this tank is 72x18x25. I'm also thinking of incorporating some live plants into the system. With that in mind. What type of lighting will I need to use for both the plants and for enhancing the color of the fish?
<Mbuna destroy plants, so they're not an option. On the other hand, other Malawians, such as Dimidiochromis and Aulonocara enjoy plants, and you wouldn't be keeping those with Mbuna. Vallisneria species are common in certain parts of Lake Malawi, so would be entirely appropriate, and in the wild Dimidiochromis hides among Vallisneria as its sneaks up on its prey, so you'd likely to get to see a very naturalistic thing if you combined them with the plants. A good approach would be to use 3-4 fluorescent tubes the full length of the tank, so you have at least 2 watts/gallon. That should be enough for Vallisneria. Substrate isn't a big deal with Vallisneria, though a mix of plain vanilla smooth silica sand (pool sand) with about 10-20% coral sand rolled in would work nicely and buffer the pH a bit.>
Thanks for your time.
<Cheers, Neale.>

Freshwater Powerheads    9/29/10
Crew,
<Matt,>
I have been reading and reading but cannot find much on powerheads in a freshwater tank. I currently have a 55 gal freshwater cycling right now with nothing more than a Fluval 305 canister filter.
<Ah yes, a good filter, and perhaps adequate on its own if the stocking load is low, but I would add a second filter to this, perhaps something comparable to the Fluval 205 in terms of turnover. For a 55 gallon tank you want 4-6 times the volume of the tank in turnover per hour assuming small to medium-sized fish, i.e., 220 to 330 gallons/hour. The Fluval 305 has about 185 gallons/hour, so either the Fluval 105 at 85 gallons/hour or the Fluval 205 at 110 gallons/hour would be a good supplement, depending on the
stocking of your aquarium.>
This canister has one input hose and only one output nozzle.
<Standard for canister filters.>
I guess my question is........is my aeration good, how much movement do I actually need, and should I find a way to agitate the surface water?
<You misunderstand. Aeration is not relevant really, it's circulation.
Oxygen diffuses into the aquarium at more or less a fixed rate determined by the surface area of the tank. Rippling and bubbling increases the surface area a bit, but neither gets oxygen down to lower levels of the
tank which is where it's needed because diffusion of oxygen from the top to the bottom is too slow. For proper transport of oxygen you need circulation that draws water from the bottom of the tank and pushes it out at the top.
Your canister filter is designed to do this, which is why the inlet goes at the bottom of the tank and the spray bar at the top. The more turnover you have in gallons/hour, the faster oxygenated water is sent to the bottom of the tank and the more quickly deoxygenated water is brought back up to the top.>
I have a few Koralia powerheads left over from my saltwater days that I can place in there if that is what I need. Any advice of help you can give me on what kind of movement and aeration I need would be greatly appreciated.
<If water quality is adequate using the filter you have, then a powerhead that provides additional water current at around 100 gallons/hour would indeed be helpful. The Koralia units can be attached at different levels of the tank, and placing one at the middle or lower level of the aquarium
would perhaps be optimal.>Thanks,
Matt
<Cheers, Neale.>

what size bulkheads holes should I drill into my tank and is a Quite One 5000 with 1330 gph overkill for 1 Black Piranha  9/12/10
Hello , I have a 75 gal aquarium that I am setting up to keep (a) Black Piranha in .
<Serrasalmus rhombeus. A potentially very large, and certainly very aggressive, if neurotically shy, piranha.>
Here is where I'm confused , I have read that piranhas need lots of circulation ( water turnover )
<Up to a point, yes. But you don't need to go bananas. Piranhas come from rivers and lakes, and they enjoy steady rather than turbulent water currents. One or two large canister filters (or possibly hang-on-the-back filters) should do the trick just fine.>
so I bought a Quite One 5000 , it pushes 1330 gph at zero ft. , now the guy from eBay where I bought the sump from said it holds 25 gal of water and from where the bulkhead holes will be drilled to the bottom of the sump
is roughly 30 inches . I plan on drilling 2 holes ,what size holes do you think I need to drill in the back top of the tank for the Quite One 5000 . I'll also have to drill 2 holes into the top of the sump lid , there is a hole there but its really small . ,,, Thank You ,,,
Rick
<If you intend to use a sump -- and it's a good idea -- then you need to go along to the marine section and read the articles there. Things like pipe sizes are discussed there.
http://www.wetwebmedia.com/plumbingmarart.htm
http://www.wetwebmedia.com/pbh2oret.htm
http://www.wetwebmedia.com/pbholesfaqs.htm
The one key difference is this. Unlike a marine tank where you need lots of water currents at different angles, most freshwater fish are used to a single strong current, e.g., the flow of a river. All you want is a steady flow, preferably along the bottom as well as the top of the tank, such that a piece of flake food released at the bottom of the tank doesn't sit there but gets whooshed along. One or two outlets at the left hand end of the tank for the water to flow into the sump, and one or two outlets at the right hand end of the tank for the water return, will work nicely. Cheers, Neale.> 

Powerhead Problems   5/31/2010
Hello,
<Ave,>
I just emailed about snails overtaking a plant tank I have set up but I have another issue that I thought I would ask about. I recently went on a month long vacation and had a friend watch my tank.
<OK.>
Long story short, my power head shut off and thus, shut off oxygen supply to my fish.
<Ah, I see.>
I never had an issue with the hang on the back filters because they automatically added oxygen but I upgraded ( I thought) to a canister filter that, as I found out later, does not add oxygen to my water.
<No, you misunderstand completely. Neither filter "adds" oxygen to the water. You really can't meaningfully "push" oxygen into water without substantial pressure. All filters, powerheads and airstones do is create turbulence and circulation, and together these maximise the surface area between the air and water, and ensure better distribution of oxygenated water throughout the tank. If your canister filter isn't doing this, then you set it up wrong! Let's be clear about that. Hang-on-the-back filters work well in terms of turbulence because they have a splashing sluice over which the cleaned water is returned to the aquarium. But the return from a canister filter can do precisely the same thing, e.g., by using a spray bar or a venturi jet return. Again, the key thing with circulation of oxygen throughout the tank is turnover -- not air bubbles -- and for that to work well you MUST have water being sucked in from the bottom of the tank and then pushed out of the filter at the top of the tank. Hang-on-the-back
filters and canister filters can both do this very well, and arguably canisters do it better because the inlet and outlet are at different ends of the aquarium. But if you don't have adequate circulation -- measured in litres/gallons per hour -- then neither type will work well.>
So I added a Marineland power head that can push water but also add air.
<Doing nothing of the sort. All the powerhead is doing is increasing circulation.>
anyhoo, over that last three years I have replaced this three times since they shut off on their own.
<Yikes. Marineland is a mid-range brand, and I'm surprised you've lost three in three years. Do check you are using the units correctly.>
One time I was going to bed and my husband noticed all my fish were at the top of the tank.
<Classic sign of poor water circulation.>
I didnt know why so I took a look and realized they were all suffocating.
I giggled the power head and it turned back on. This is a common theme with these things.
<So why keep buying them? One reason I advocate, for example, Eheim gear is that despite being relatively expensive, these German units have exceptional reliability, their products routinely working for 10 years or more.>
So, back to my story. Half way into my vacation, it shut off after she did a water change and 8 hours later 40 out of 50 fish were dead. angels, gouramies, knife fish, black skirts, Neons, loaches, etc. ( yes, you may cringe at the variety of fish that may not be compatible but surprisingly, I never had any issues with any of them.
<Indeed.>
If so, I would have found them a new home to keep the peace). I was heartbroken and completely sobbing because they were my pets. My question is, is there a particular brand that you would recommend to replace this?
<Do first understand what it is you're trying to do. If you're using a canister filter, for a heavily stocked tank you're after a circulation around 6 to 8 times the volume of the tank per hour; i.e., for a 55 gallon aquarium, not less than 6 x 55 = 330 gallons/hour. That's quite a large canister filter; even the big Eheim 2217 canister filter is only 264 gallons/hour, so for effective water circulation you'd probably need two canister filters. On top of this, you need to make sure the canister filters were arranged properly, with the inlet at one end and the outlet at the other, and with a jet return or spray bar that's splashing the water about at the surface. Note that fish like Gouramis aren't wild about strong water currents, whereas Black Ghost Knifefish come from shallow rapids and absolutely must have strong water currents to survive for long, so you would arrange and install filters based on the types of fish you're keeping.>
We have added two bubble wands hooked up to a air pump for now but I would like a second option in the future. I bought an AZoo that is still sitting in the box because I'm so afraid to have only 1 air supply in case that shuts off. What do aquarists use for their air supply with a canister filter?
<You don't "add" air; you make sure the canister is [a] sufficiently big for the job; and [b] arranged such that it's creating the right circulation and some degree of splashing at the surface.>
Thanks for your help
Lisa
<Hope this helps. Cheers, Neale.>  

Re: Powerhead Problems  6/1/10
Thank you for your quick reply Neale.
<You're welcome.>
The powerhead I keep buying is the only one I have readily available. I am a U.S. Military wife located outside of the United States and items such as these are considered "nonessential".
<Indeed?>
So the store on our base only carries this one. By the time my power head goes out, I am scrambling to get a new one, thus that's why I keep buying them.
<Something for your Christmas list, perhaps?>
I did order an Azoo brand to see if that would work better but my vacation prevented me from setting up the new powerhead in time. As for my canister filter, the directions for this thing were at a bare minimum.
<Oh.>
I had run into several problems/questions that either your website, the supplier or the manufacturer had to answer for me to be able to understand this product as well as how to set it up properly.
<I see.>
The oxygen that is added is understood as you had written it.
<Good.>
It is not merely added up integrated into the water via agitation.
<Precisely. What agitation does is create ripples, and these increase the surface area where the water is in contact with the air. But this effect is still relatively small compared to the value of adequate circulation of the bottom layer of water up to the top of the tank.>
The Marineland canister filter I have is a C-530 for up to a 150 gallon tank. It pumps 530 gph and is quite forceful with the water output tube.
<Indeed.>
I bought two of these for my 150 1/2" acrylic I am in the process of putting together and set one up for my 55 gallon so I can become accustomed to how it worked before I set up my larger tank. Because of the amount of
water it puts out it is quite loud when placed at the surface of the water.
<Yes, but the noise of the splashing is surface agitation, and precisely what you want. At the least, you want the spray bar rippling the entire surface of the water.>
The tank is in our living room behind our couch so it makes it difficult to enjoy a movie or to read a book.
<I understand.>
That is why I added a powerhead to try to agitate the water.
<Yes.>
It will be another couple of months before I get to set my large tank up because of an up and coming move so I am forced to leave what I have.
<I see.>
At this point, to have the output pointed at the surface is not an option because of the noise, so are the 2 bubble sticks (approx 6" in length each) and the horrible powerhead sufficient or is there something else I should be doing that I have no idea about.
<Assuming the aquarium is not overstocked, and that water quality is good, aeration or lack of it shouldn't be a killer. So go back and make sure your aquarium is stocked sensibly. If needs be, send me a list of what's in the
aquarium and how big the aquarium is. Also check the aquarium isn't too warm; oxygen concentration drops as temperature rises, and for most species 25 C/77 F is the optimum, but many fish actually need slightly cooler
conditions. Check water circulation throughout the tank is good, especially at the bottom, e.g., by placing something like a bit of lettuce at the bottom of the tank and seeing how thoroughly and quickly it gets whooshed
about the tank.>
Thanks
Lisa
<Cheers, Neale.>

Water flow in large aquariums   10/30/09
Hello WWM,
<Howdy Jim>
As always I value your expert opinions so once again I am seeking your advice. I recently purchased a used 215 Gallon aquarium that previously was setup for salt water use. It has built in overflows and came with a Wet/Dry filter with Bioballs and a Pan World 200PS pump (1750 GPH). After redoing all the overflow plumbing that had been cut I was ready to do some testing.
During my initial tank testing, I filled it up and turned the pump on and the water flow was tremendous, but because it only has two ¾� loc-line nozzles for return water it creates massive currents in the tank. Currents so strong it was moving my substrate around and making piles with it! LOL!
Now for a salt water tank I know that is desirable, but for freshwater tank it seems a bit much. I read a post where WWM gave a formula of 8 X (gallons of tank) for calculating water circulation. This formula puts me at 1720 GPH so I am just a little over with my pump. But I guess my overall questions are:
1. Does the formula apply to larger aquariums?
<Yes, does>
2. Will that amount of water flow hurt community fish such as Angels, Neons, Silver Dollars, etc?
<Might be too vigorous as it is currently arranged... I would look into removing the Loc-Line fittings (possibly the bulk-heads as well) and fashioning/fitting some "regular PVC" tees et al. to make the flow less directed/forceful. IF this doesn't fix the issue, possibly adding either other throughputs (through the tank or over the top) is in order>
a. If it will harm the community fish, I was thinking of switching to a smaller Pan World pump (750 GPH model). But a question here would be the current pump has 1� plumbing, the new pump has ¾� plumbing fittings. Will I need to change the existing plumbing again to downsize, or can I reuse current plumbing and just use adaptor fittings to reduce/expand at the pump?
<You could even just add a restrictor valve (ball, gate) on the discharge of the current pump... but I'd do what is detailed in #2 above>
b. If it will not harm the community fish, I was thinking of taking some pipe and drilling holes in it, cap it at the end, and use that to diffuse the return so that it doesn't create that massive jet of current that moves everything around.
<Ahh, another possible approach>
i. Does this seem like a viable option to you? And could you share any other tips you might have about diffusing the currents with that high of a flow rate?
<Have done so>
ii. Will it hurt the pump if I restrict the flow?
<Only if extremely restricted... if cut to about half, only some appreciable increased waste heat should be expected>
I am concerned that with drilling holes and diffusing the flow that I may restrict the flow and it will damage the pump. Should I be concerned about that?
<No>
3. With a 215 Gallon tank is there a minimum circulation that I should shoot for as well?
<Enough to keep the system functional, attractive. I do think the current pump is about right. You just need to modify the discharge plumbing>
Thanks again for all your help and advice,
Jim Odom
<Welcome. Bob Fenner>

Re: Water flow in large aquariums -- 10/31/09
I have to give you guys a HUGE thank you. I have searched the web on countless occasions to find information and honestly, it is all over the place with answers, but you all have always been consistent and spot on! It really is nice to know that I have a place to go when things just don't quite make sense and the local pet store doesn't have a clue.
<We share!>
BTW, I will follow your advice here and build out a "diffuser" for the flow.
Thanks again,
Jim Odom
<Welcome Jim. BobF>

Water flow on tank bottom   8/22/09
Hi Neale,
<Don,>
I changed the subject line and deleted all but the pertinent part of the last email to shorten this email, but this is still about ghost shrimp losses.
<Fair enough.>
Re your comment on water flow and oxygen near the gravel bed versus top of tank: We have lots of surface disturbance and water currents now with 3 strong power heads outlets (corners/middle) shooting water within 2-3 inches under the surface of a 2 feet deep 120 gallon tank. The two Fluvals suck from 6 inches off the bottom and discharge 6 inches from the top. Our feeding flakes do slowly drift over parts of the bottom as just tested.
<So long as the flakes move rather than collect, you're basically fine, though mountain stream fish (like Hillstream loaches) and perhaps shrimps may prefer/need stronger water current. Depth of the tank is maybe an issue; things like shrimps and Corydoras are adapted to shallow water, and in tanks more than, say, 12 inches/30 cm, they can have problems.>
Would you suggest cutting 1 or 2 of our 3 power head uplift tubes in half, thereby shortening them, which will lower the power heads way down in the water column and create much water movement in the middle/lower part of the tank?
<You could do this if you wanted. An alternative is simply to use a spray bar or venturi that directs water current 45-degrees downwards rather than flat across the surface.>
Will this affect over all oxygen content in the water, as I thought that it was surface disturbance which put oxygen in the water?
<No, it's not the splashing at the surface that is critical, though yes, the more splashing, the more CO2 leaves the water and the more O2 is absorbed. It is mostly circulation of the oxygen-poor bottom layer of water up to the air/water interface at the top that is critical. Oxygen is mostly added to water at the top, by diffusion. In the best tanks, like marine reef systems, you'll see water inlets at the bottom as well as further up that drain water into the sump, so water can be sent back up to the surface of the tank via a powerhead or whatever. While that isn't always practical in a freshwater tank, resting a small internal canister filter, a
powerhead, or even a decent airstone somewhere it drags water from the bottom and upwards towards the top can help. Airstones, by the way, are like water "elevators", the bubbles pulling water to the surface.>
Follow-up info for you: No copper meds have ever been used, and our pipes are PVC plastic for culinary water.
Many thanks in advance,
Don
<Hope this helps, Neale.>

Re: Water flow on tank bottom   8/22/09
Neale, thanks once more. We clobbered this subject thoroughly. I learned a lot and hope it helps others.
Cheers,
Don
<Glad to have helped. Good luck with your fishkeeping! Neale.>

Water Movement, gen. FW, Angelfish sys.  -- 01/22/09 Hello Crew, Hope all is doing well. I have a question about water movement please. I have been doing quite a bit of research of why it is necessary and all of the benefits. I have a 75 gallon freshwater tank with an emperor 400 power filter. Because of all I read about the importance of water movement (and to help clean my substrate) I have ordered (not received) 2 #2 Koralia water pumps. I have read that these do not shoot out sharp streams like some power heads, but more of a wide less powerful flow. Now I am starting to read some articles about how some fish actually will not do well in aquariums with water movement such as angelfish. Although I have no fish in my tank yet as it is cycling angelfish was going to be my first choice. Please help me know which fish I should not get because of water movement. Is it true that water movement is detrimental to angelfish? Thank you for your help. James <James, water movement is important for many reasons. The main three are these: even distribution of heat from the heater; cycling of oxygen from the surface to the bottom of the tank; and movement of ammonia and nitrite through the biological filter. Additional benefits include giving the fish exercise, moving solid wastes through mechanical filters, and keeping plant leaves free of detritus. In general terms, most community fish will do well in tanks with water turnover rates of 4-8 times the volume of the tank per hour. Add up the turnover from all the filters and pumps in your system, and if the total is less than 8 x 75 gallons = 600 gallons per hour, you should be fine. Yes, Pterophyllum (and indeed most laterally compressed cichlids) do not enjoy turbulent water flow, but strong, steady water flow will not harm them. If you ensure that there are some tall, upright bogwood roots in the tank, these will acts a baffles and create less mobile pockets of water, and your fish will congregate there if they need a rest. Cheers, Neale.>

Re: Water Movement Thank you Neale, I just found out that the Hydor Koralia Water Circulation Pumps I ordered supposedly have a flow rate of 600 gph each. That in addition to my emperor 400 (which probably only pumps 300 gph with media inside) is going to be way too much. How do other aquarium owners get by with having strong power heads going in their tank in addition to their regular filter? Thanks again. James <Hello James. Don't put too many pumps in the tank. While some fish actually adapt rather well to very strong water currents, Mbuna for example, Angelfish won't thank you for it. Try installing just the filter first, with just one circulation pump, and see how things go. There's no advantage to having too much water current if your fish will be stressed by it. Cheers, Neale.>

Re: Water Movement Hello Neale, and as always thanks for your advice. After our last e-mail I have been considering adding another emperor 400 to the other side of the tank for a more even water distribution. I know another filter would balance things out and keep the water flow more rapid (probably about a 600 gph turnover with both pumps going. In your opinion would you do this and leave out the other Koralia pumps I mentioned or leave in just the one power filter and use 1 of the Koralias? I want the most water flow along the bottom for detritus to move into the water column and I don't know which of the combinations would be best. Also, If I continued using just the one emperor filter and added 1 Koralia what do you think the placement would be? I know I am probably being too picky, but I want to make a new start the right way and I know from all I have been told by you just now important water movement is for a cleaner tank and happier fish. Thank you again and have a great weekend! James <James, all else being equal, your water turnover "budget" is best spent on filters. In a marine aquarium, water movement pushes water past the live rock, where it gets filtered, so adding powerheads and water pumps will indeed improve water quality. But in a freshwater aquarium all a powerhead does is push water about. That helps with oxygen and heat distribution, but has no impact on filtration. So for freshwater aquaria, while you certainly can add powerheads, it's not worth doing so INSTEAD of adding additional filters. That said, hang-on-the-back filters have pretty sucky performance when it comes to moving water about along the bottom of the tank because of their design, though this varies from model to model. I don't use them, and they aren't widely sold here in the UK, so I can't speak from experience. But I suspect you'd find at least one powerhead pushing water along the bottom of the tank quite useful. Cheers, Neale.>

Re: Water Movement, FW  1/24/09 Hello again Neale, A couple of e-mails ago you mentioned that I should add up all the gph from all filters and power heads and make sure they did not go over 600. But since my filter is a hang on the back couldn't I discount that as far as adding to currents too strong for fish since it does not move the tank water much? Thanks again, James <Hi James. The short answer is no, you shouldn't remove your filter's turnover from the overall turnover estimate, at least not at first. It may well be that once your tank is set up you'll find dead spots in the tank (flake food doesn't move, plant leaves don't sway, detritus sits on the sand). Then you can add additional pumps as required to supplement any issues specific to the filter types being used. But initially, you don't want to expose your fish to extremely high levels of water movement that they might not be adapted to. Cheers, Neale.>

Re: Water Movement 1/24/09 Dear Neale, please forgive me for continuing on this issue, but I have gotten a little confused. <Oh?> You mentioned the total gph turnover safe for fish movement in a 75 gallon would be up to 8 times the volume (75) which would equal 600 after I added up all my pumps output. <As I've said *it depends on the fish*. Surf-zone cichlids like Eretmodus or Hillstream loaches such as Gastromyzon would be happy with 10, 12 times the volume of the tank in turnover per hour. On the other hand, Angelfish would be better at around 6 times because they come from more gently flowing rivers, and tank-bred fish especially won't be used to torrential flows of water.> Like I have said before I prefer hang on the back filters because I have used them before and also because the way the cabinet under my aquarium is constructed I cannot use a canister filter because of the room constraints. <Fair enough. But whether you like them or not, and I appreciate they have some useful attributes, they aren't great filters for messy aquaria because the inlet and outlet are so close together.> If I use 2 of the emperor 400s that will be about a total gph turnover of about 600. So if I still have food and detritus on the bottom that does not move with both of these pumps operating you feel I should not add a power head to assist because of the extended amount of gph turnover? <I would certainly NOT add another pump (or filter) until you'd set the tank up with these two Emperor 400 units and seen how the fish react. If they're fine, and the water movement is not turbulent, you may want to add one or more strategically placed pumps elsewhere in the tank. My community tank operates at 8 times the volume of the tank in turnover per hour, and despite what you might think, the water flow isn't all that strong once the filters are filled with media and the tank decorated with rocks and plants that break up the water flow. But certainly try things out as they are first, and then make decisions about adding more pumps. Without seeing the tank or the decor, I can't predict precisely how the water is going to move about in this aquarium.> Is that correct? Thank you again. James <Cheers, Neale.>

Water Flow Too Powerful    12/18/08 Hello, I have a 30 long tank with just 3 mollies and about a dozen fry. My penguin 350 is too powerful for my fry to handle. However, it is ideal for the load of fish I plan to fill this tank with in the next 3 months. The fry will eventually be moved to a 30 hexagon to grow up in but I haven't started the set-up for this tank yet. In the meantime, is there a way to slow down the output water flow without compromising the efficiency of the filter? This is how I'd like to stock the 30 long: 2 Black Mollies (already in tank) 2 Silver Mollies 2 Cremecicle Mollies (1 already in tank) 2 High Fin Swordtails 2 Red Wag Platies 2 Rams 3 Corys Can my filter handle this bioload, without the fry? Audra <Try directing the outflow from the filter towards the glass instead of into the tank; the current will disperse, and the fish will be less "pushed about". Some of your fish enjoy strong water currents though, in particular the Swordtails and Corydoras, so they won't care. As your research should hopefully reveal, Mollies usually do best in tanks where salt is added, and while the Platies and Swords won't mind, the Corydoras and the Rams may well do. On the other hand, Rams need very warm (28-30 degree C) conditions, and that's much too hot for Swordtails, Platies and Corydoras. Keep the Rams too cold and they'll get sick and die. (Actually, most commercially bred Rams die within weeks anyway, and they're a fish I simply don't recommend unless you're able to buy locally bred or wild caught stock.) So over time you'll likely want to spread out your stock into tanks best suited to the needs of these various fish -- while they might be fine now, by imposing on the preferences of each species, you increase the odds of disease and poor health. For now, I'd SERIOUSLY consider keeping JUST livebearers in this one tank, maintained at about 25 C (77 F) and with a little salt added (say, 3-6 grammes of marine salt mix -- not tonic salt -- per litre of water). This will suit Mollies, Guppies, Platies and Swordtails. There are various salt-tolerant fish you could add, about which we can discuss another time. But since you're still stocking the tank, I'd heartily recommend choosing carefully now, rather than trying to fix problems later. By the way, all Mollies cross-breed, so if you want a single "sort" of Molly fry that you can share or sell back to pet stores, keep JUST ONE variety in the tank. Pet stores don't really want "mutt" Mollies that aren't any one variety, and after a while you'll be fed up with housing hundreds of fish you can't sell. Cheers, Neale.>

Re: Water Flow Too Powerful  12/18/08 Thank you, Neale, for your feedback. I'll take everything you said into consideration. <Audra, I'm happy to help. When planning an aquarium, it's wise to be prudent, and take into account the needs of all your fish. Doing so is the path to easy, low-maintenance, healthy fishkeeping! Just because Rams won't work with Mollies, doesn't mean you can't keep *any* dwarf cichlids. Consider Etroplus maculatus for example, or one of the Pelvicachromis species such as P. taeniatus. Get back in touch if you want some more ideas. Cheers, Neale.>

Water or air Pump, for moving new water for FW sys.  11/17/2008 Hello all, <Hello right back!> Hope things are going well. <Not bad, thanks for asking> I have a question about an air pump, please. I plan on keeping fresh water for my water changes in a large plastic trash can. I would like to know the smallest water pump that would be sufficient to keep the water circulated. <Assuming you mean an AIR pump to keep the water AERATED? Then you essentially answered your own question - How big a pump do you need to push the air down an air tube to the bottom of the trash can where it is then released into an air stone?> <If you're talking about a standard 35 gallon trash can you'll find that the smallest and least expensive pumps found in the average pet shops won't do the trick as they usually start to lose pressure after 14 inches or so. Also, the larger the pump, the less stress on the diaphragm for pushing the water that deep. I've used a 1 inch piece of PVC pipe with a 90 degree elbow at the base and places the air tubing inside that, approximating the lift tube of an under gravel filter to achieve the same result. Keep in mind that the purpose of the process is to lift water from the bottom of the tank to the top where it exchanges gasses at the surface -- the amount of gas exchange directly between the water and the air bubbles is not significant.> <Which brings me to a WATER pump designed to CIRCULATE the water. In that case you can purchase a very small water pump - like the kind they use in decorative desk fountains even - and place it on the bottom of the tank with any kind of output tube that at least creates ripples on the surface. I use a bigger pump... big enough pump that when it comes time to do the water change, I just add a hose extension to the pump and pump the new water directly into the tank in the next room. To save energy I put it on a timer and it circulates for an hour every 6 - and then on manual for an hour before water change.> <The UP side of the air pump solution is that you are pumping fresh air from outside the container to the inside and need only a small vent hole to allow air to escape. The down side is noise. The UP side to a water pump is less noise and more utility, the down side is that you have to have more venting (to allow fresh air exchange at the surface) which means more evaporation.> Thank you for all your help. <Opinions, yes -- help, you tell me.> James Hall <Regards, Darrel>

Water movement... FW... book time...   10/17/08 I am setting up a 75 gallon freshwater tank and will be using several large power filters. I would like a suggestion on what to use to cause enough water movement at the bottom of the tank to cause the waste to mix with the water so it can be removed by the filter. I know there are air pumps and powerheads all different sizes, but I have no idea what and what size to use. Obviously I want it powerful enough to move the waste but not so much as to cause too much turbulence. <External canister filters are the best filters for large tanks. You can arrange the inlet pipes and outlet spray bars at different ends of the tank, ensuring good circulation. Provided the filter (or filters, added together) give a turnover rate of not less than 4 times the volume of your tank (i.e., 4 x 75 = 300 gallons per hour) and ideally 6+ times the volume of the tank, your filtration system should be fine. Undergravel filters can be good, but again, you'll want a powerhead at each end to ensure good circulation, and these filters are not compatible with sand, plants, or the use of large amounts of rock. Personally, I consider hang-on-the-back filters to be poor choices for various reasons, not least of which is their limited flexibility when it comes to filter media options and the fact the inlet and outlet are close together, making it difficult to ensure thorough circulation. Cheers, Neale.>

re: water movement... abusing WWM If I use only power filters what would you suggest to add for good water circulation? A pump or power head on the bottom? <Properly arranged external canister filters will take care of filtration AND circulation. Much material on WWM about filtration and circulation. Cheers, Neale.>

Re: problem with aquarium system, disease... emphysematosis, induced... no reading   7/8/08 Hi, The system is run by a 1 hp pool pump. <... For this many gallons? Why? You want to read/look into a better, non-high-pressurized pump... this one will "drive you into the poor-house"... See WWM re Pump Selection: Here: http://wetwebmedia.com/ca/volume_3/cav3i2/External Pumps/External_Pumps.htm and the linked files at the bottom> There is a lot of air/water mixing in the strainer chamber so i guess there is pressurized water there. <... yes... this is along with the improper pump, the cause of the trouble here> Is there a possibility of having too much oxygen in the water which is causing "the benz"? <As in Mercedes? Yes> i notice that when the fish were removed they recovered quickly in a medical tank using MelaFix. <... you're joking right? Ridiculous> the water renters the tanks through 1" tubes emptying by the top and there are fine bubbles in the return water into the tank. The bubbles on the fish though are coming through their skin, not attaching to them. The pH is 8.0 (African cichlids) ammonia is 0, nitrite is 0. Thanks! Don <... read here: http://wetwebmedia.com/PondSubWebIndex/PdBblDisease.htm and the linked file related at top. BobF>

Re: problem with aquarium system, disease... emphysematosis, induced... Thanks for all the help! I'm off to shop for a new pump! Don <Ah, good! BobF>

Pump Position on Ocean Clear Filter 5/21/08 I am considering using the ocean clear 325 and 318 connected to my 75g Discus tank. I don't understand from the RED SEA mfg instructions, <Me neither.> should I put my Quiet One 4000 water pump before the canister filters pushing thru or on the other side of the filters pulling water and returning it back to the tank. Please reply... thanks for your help, Dan C. <You will want the pump to push the water through the canister. Having it pull the water through will restrict the intake, a bad thing for these types of pumps. Welcome, Scott V.>