Rocks or gravel on the bottom? Gravel is not good in the bottom of a pond unless you are using an under-gravel filtering system. Rocks, on the other hand, can be used to make caves for your fish to hide in. I used gravel one time and after cleaning out the pond, only put gravel on top of the pots that the plants were in.

Hi I am in zone 5 also and built my first pond 4years ago.. I consulted my local pond company and was told to put small rock not gravel on the bottom so that is what I did and haven't had any issues to date. I also have a skimmer box that houses my pump and a filter,along with a waterfall box with filter. I have a friend who didn't put rock in the pond at all and always has green water??? I know some will chime in about no rocks but I'm going with what works for me . My pond is 1500 gallons with koi,goldfish and plants.

Well, that isn't because there are no rocks in the bottom. The green water may be a sign of an insufficient filtering system or no balance of fish and plants or both.

They said rocks would be on the bottom. NOt so much for the fish to hid but I think more for eco of pond.
Does anyone still use the lava rock bog for thier filter system?
If not what do you use?

I use a waterfall filter (Atlantic Filterfalls) as well as a bog filter. By bog filter is above the pond level, next to the pond, about 7'x4'x11", filled with pea gravel and has plants on top. Also use a UV sterilizer in my skimmer. I have no issues with green water but do get string algae from time to time.

Jeannie01,
Let's talk a little about bacteria. There are two types of bacteria that can live in your pond. One requires Oxygen and one lives without Oxygen. So how can bacteria under water get Oxygen? The answer is that small amounts of Oxygen is contained in water and the bacteria is able to get this Oxygen out of the water. With that in mind lets take a look at a pond with either rock or gravel on the bottom of the pond. If I was locked up in an air tight room at first I would be fine as there would be plenty of Oxygen. But I would slowly that Oxygen would be used up and unless fresh air was let into the room I would die from a lack of Oxygen. Now keeping this in mind lets look at the bottom of a pond. The bacteria living in the rock or the gravel on the bottom of the pond needs Oxygen. The only place the bacteria can get Oxygen is from the water. The bacteria will slowly use up the Oxygen in the water that it is in contact with and die unless new water is moved into all the areas that the bacteria is living in. Let's now look at how this fresh water is going to get to the bacteria. Water in a pond doesn't move unless something moves it. Lots of things can move water in a pond. It could be a simple as wind blowing across the surface of the pond. Yes the water at the surface is moving but the deeper you go into the water the less the water is moving. This is also true of most pond's pumping systems. The water is removed at the surface and put back in by waterfall at the surface. The deeper you the less water movement. So at the bottom of a pond what water movement do you have. Unless you have a very shallow pond or a mechanical devise moving water at the bottom you have one thing moving water at the bottom and that is fish or frogs. As these swim they do move some water. Now you have rocks or gravel on the bottom. Yes as fish and frogs swim they are going to move some water at the surface of this rocks and gravel but they are not going to move much water between the rocks and gravel. Then you start to get debri on the bottom and less water moves between the rock and gravel. The bacteria that requires Oxygen to live in these areas start to die from a lack of Oxygen. Can the bacteria that does not need Oxygen do what these die bacteria use to do? Yes and no. In the lab they can grow these bacteria and they do a better job then bacteria that require Oxygen. But no body has been able to grow these bacteria outside the lab with any success. In the real world these bacteria do far more harm then good. Now that we have looked at some of the down side of rock or gravel on the bottom we can look at the upside. Yes at first it looks better then a bare liner. Also the rock on the top sides of the rocks does provide more surface area for bacteria to grow on. Assuming that we can keep the debri off the rocks or the bare liner we will grow algae. The amount of algae growing on the two system isn't much different. The good bacteria isn't going to grow at the very base of this algae because of the lack of Oxygen but on the algae itself. So after a period of time both systems are going to have about the same amount of bacteria in them. They are going to look about the same. But the area for bacteria that doesn't need Oxygen is going to higher in a pond with rock or gravel on the bottom. That is the reason that a pond that has rock or gravel on the bottom needs to be emptied and cleaned.
Then you asked about bags of lava rock in filters. I assume you are talking mostly waterfall filters. First we have to take a look at why bags of lava rock was put into them. Normally the water came in the bottom of the box and then was to go up through filter pads and then through the bags of lava rock and then out. When they new or just cleaned most of the water does just that. One of the thing these filters are suppose to do is to catch debri. As they do that it easier for the water to go around the pads then go through them. Once it goes around the pads is it going to go through the bags of lava rock? No because it is easier to go around a bag then go through it. So why is there bags of lava in these filters? If you remove them what happens? The water coming in the bottom of the filter just pushes the pads up instead of going through them. So the reason why the manufacturer put the bags in the filter was to hold the pads down. So why lava rock in the bags instead of gravel? Two reasons, one the consumer thinks that the lava rock is going to have more surface area to grow bacteria but water isn't getting to that surface to grow good bacteria. Secondly lava rock is lighter then gravel and layer on the pads would be too heavy to remove or distort the pads too much. In other words they were used as a weight to keep the pads in place.
I am sorry for such a long post.
Mike

Wow Mike, that was an extremely informative post I'm glad to have read it! You answered questions I've always had but was too shy to ask. Keep them coming! thank you leigh

Leigh,
No Leigh thank you. After going back and rereading my post I am surprised anyone could anything out of it as poorly as it was written. Never be too shy to ask a question. We all learn by questioning and then by getting or finding the answers. When we stop questioning we stop learning.I am happy to answer any question that I can only I suggest that they get posted on their own thread as it is not fair to Jeanne01 to tie up her thread.
Mike

when building our 14x16x4 pond we originally used 6" river rock on the sides and bottom. After a short time the water became cloudy and we couldn't clear it no matter what we did. We finally drained it and could not believe the muck and debris accumulation between all the stones. We took them all out and have enjoyed a crystal clear pond ever since. Rocks are just traps for muck and yuk IMHO.

I like to do what they call a hybrid pond, if you are looking for the latest thing. Basically a hybrid pond is a mix of more advanced filtration like you would have in a koi pond with the look of a watergarden. Also a hybrid pond isn't as complicated as a koi pond but borrows some of the water quality tips like rockless bottom, bottom drain, skimmer, filter, UV light.

I don't put rocks on the bottom but I do put them on the sides and shallow areas. Really after awhile you get enough algea you can't tell there aren't rocks and this absolutely is the number one thing to do to keep your water happy and beautiful!! As for filter you could do a bio or mechanical or combo of the two. I think a skimmer is a must. If you want to get really fancy you could put in a bottom drain to make clean up and water quality even better. If you don't want to build a settlement chamber you can run it to your skimmer.

Good luck!

I agree with a lot of what evesta says with the exception of running a bottom drain to a skimmer. Let me explain why. Most bottom drain to skimmer hookups use 2" pipe because of the lack of room to connect a larger pipe. The weir size on skimmers range from 6" to 16" wide. So the only head pressure that is going to determine how much water is going to come from the bottom drain is the amount the pump is going to be able to lower the water level in the skimmer as compared to the pond level. On a skimmer with a 8" weir the skimmer manufacturer is going to recommend a pump no larger then 4000 gph. So if I figure a 8" weir with a 4000 gph pump the drop in the skimmer is going to be about .5". With a 2" pipe from the bottom drain there is going to be less than 600 gallons per hour. Yes this is enough flow to circulate the bottom of the pond water but is not enough to move much debri from bottom of the pond to the skimmer. But it is enough to keep debri from moving from drain area on the bottom of the pond. What will then happen is that this debri will clog the drain until you have very little water moving through the drain. It is a nice marketing tool but in the real world doesn't work very well. I know that there are going to be some that say their drains have a greater flow then this. They will say that when they close the skimmer door and the water level in the skimmer drops down to where the bottom drain line comes into the skimmer and the flow is lot faster then listed above. And they are correct. If the level has to drop 6" to get the entry point of the drain line then the flow would now be about 2150 gph. But this is not the water level in the skimmer under normal operation.
Mike

I agree Mike. It would be better not to run it to a skimmer but I know it can be done and is better than nothing. I used a settlement chamber in my old pond but am toying with the idea of doing the skimmer thing on my new pond build because of lack of room for settlement. I was even thinking of not putting in a bottom drain but it was so nice to have even if installation was a bit more complicated. This time I'm not having any koi and my pond will be smaller so I thought maybe I'd just vaccuum but I just don't know. Any ideas for me? Thanks!

Evesta,
Personally I would use an external pump with the pump sucking from the skimmer and the bottom drain. A ball valve on pipe going to each devise. The basket on the pump will catch most of the debri from the bottom drain and the skimmer will catch the debri from the surface. By having valves on both inlets it will allow you to increase or decrease the suction at each devise.
Mike

Cool. I actually have a lot of left over things from my old pond and one is an external pond master pump with basket. I also have a Oase skimmer already and a waterfall filter. Pretty much just need to get a new filter, bottom drain and liner.

Do I need to dig a pump pit or can the pump be at ground level? I would like not to because of space issues and tree roots in the area I want to hide the pump and external filter, sort of behind the waterfalls.

The PondMaster pump has to be flooded suction so it would have to be below pond level.
Mike

For a pond that size, I’d focus on getting the filtration right from the beginning rather than making the setup more complicated than it needs to be. A good biological filter helps beneficial bacteria break down fish waste, while mechanical filtration catches leaves and other debris before they build up. Rocks on the pond bottom can look natural, but they can also trap waste and make seasonal cleaning more difficult, especially if you’re used to a pond with a bog filter.

I’d keep the bog filter idea on the table, since your previous pond worked well with it. A properly sized UV system can also help control green, cloudy water caused by suspended algae. An Aqua UV Sterilizer is one option worth looking into. With goldfish, plants, and cold winters in zone 5, make sure the pump and filtration setup are suitable for seasonal conditions.