Reservoir Trouble, Help!

DTW.pdf (321.6 KB)
Hello Good People,

I’m attaching a diagram showing my Drain to Waste set-up. This is my first attempt at hydroponics and overall I’m pretty happy with the way things are going on this 44th day of my autoflower grow.

Unfortunately it isn’t all happy news. So I’ll give a run down on the issues I’m having; I fill my 20 gallon reservoir. Add my nutrients, adjust the PH from 5.5 to 6.3, check my ppm’s and ec as well as nutrient solution temperature.
The temperature at the fill-up is about 75 deg F. I’ll drop three 2 liter frozen bottles in right after fill up, then every 6 to 8 hours I’ll rotate a new frozen bottle. So on average my nutrient solution runs between 69 to 72 degrees F.
As you can see from my diagram I have a circulation pump that runs full time pumping the solution through a filter bucket with Bio Balls. Not shown is an air pump with two 4 inch diameter air stones. So at this point all is well but after a couple of days the nutrient solution becomes cloudy and the PH becomes very unstable. By the third day there is visible bio sludge so at this point I’m draining the reservoir and starting over. I was hoping I could go 6 to seven days without a reservoir change-out but I’m not even getting half that.

So I’ve tried using Hygrozyme, Pond Zyme and Stress Zyme all with no real improvement. I could really use y’alls help on solving this issue. At this point I may just go back to growing in soil, but I hate to quit at this point, like I said overall pretty please with the grow. I’ll be tweaking my nute schedule for future grows. If I stay growing Drain to Waste I’ll be looking to weed out a few bottles, to many bottles!

Hope y’all can help, if you need more information please ask.



Biosludge? Like diatomes? Is your reservoir lightproof? Even at low temps algae can still form, especially given a little light.

I use Calcium Hypochlorite (pool shock) in small amounts (~40ppm) in my reservoir to keep the sludge at bay.

Hydroponic grade peroxide is also effective in controlling such things.

You can use a combination of both to cover a broader spectrum, or alternate between them.

There are commercial products available as well like Clear Rez but they are overpriced for what’s in them.


So I used the term “biosludge” for lack of understanding just what it is. I can tell you it is an off white gelatinous matter that appears as clumps and left unchecked it will stop up the impellers of my pumps. I also forgot to mention that I do use hydroponic grade H2o2 at a rate of 2.5 ml per gallon. However I have no idea if that’s to much or not enough.

My reservoir is white, I keep a lid on it and the reservoir sit’s on the bottom shelf under a grow tent away from any light source.

I’ve never heard of using Calcium Hypochlorite in a reservoir but I’m willing to give it a try. You say you use it in small amounts (~40ppm). I’m really going to show my ignorance here but how would I measure that? How much would I need per gallon?

Thanks for your help.



Not enough. I use 5ml per gal (of the 30% stuff) and I find that not strong enough when things get really slimey.

It definitely sounds like algae, but that usually has a brown, green or yellow color. But it can be clear and grayish too, and will form an oily like film sometimes.

If you’re adding enzymes and they also arent helping it could also be some type of congealed sediment, either from hard water (unlikely) or mineral based fertilizers.

As for pool shock and the PPM question I put in about 1.5g per 5gal which equals out somewhere around 40 parts per million. A PPM/EC meter is a great tool to have to accurately measure the amount of stuff you’re mixing into your water and be able to repeat it as units like grams/teaspoon/ML are hard to get things exact.

Edit: oh another thing I should mention is that water tends to run back into the reservoir from your drip lines between watering taking with it any diatomes that formed inside the tubing since last irrigation cycle. Do you wash and scrub out your reservoir every time you fill it? Not saying you should do any of those things, but those are just some of the ways diatomes can form. The biggest factor in my experience is the water in the reservoir being exposed to light. Even a little bit coming through a crack or a hole will give algae a chance to grow.


Thank you thank you. So I’ll up my H2o2 to 5ml per gallon and I’ll pick up some Pool Shock and try that as well. I do have a PPM and EC meter but need to fully understand the complexities of EC and PPM, I have a lot to learn.

So I have wondered if it’s actually my nutrients causing this gelatinous matter? I’m actually embarrassed by the amount of ingredients in my nutrient solution. I’m using 10 different bottles! I feel like a fool every time I look at them. I’ll list below what I’m using.

  • Sila Guard (dutchmaters)
  • Cal-Mag (dutchmasters)
  • Flora Micro (GH)
  • Flora Grow (GH)
  • Flora Bloom (GH)
  • Koolbloom (GH)
  • Diamond Nectar (GH)
  • Saturator (dutchmasters)
  • Rapid Start (GH)
  • H2o2 34%

So that’s quite the list. I’d love to find a one or two part water soluble fertilizer that would replace all of the above. Not that I’m unhappy with the way my plants look, I have a G14 that I’ve grown before and this looks better than any G14 I’ve grown in the past. But cost wise, well I’m paying for it to be sure.



I completely drain and wash out the reservoir, I clean the pumps and outside of all the lines inside the reservoir. I also spray a bleach solution inside the res and pumps then rinse four or five times before refilling.

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Wow that’s good that you’re patient enough to do that, I usually just rinse it all off then refill hehe.

Check out MegaCrop we have a thread here on OG too:

I’ve used large regiment nutrient programs before like yours and they work great, but are often overpriced and heavily diluted. Half the stuff is unnecessary but they usually formulate it in such a way that you have to use them all in conjunctioknor you’ll be missing something important.

On the subject of your PPM meter, it’s best to look at them as a means to repeat a specific dosage.

So say you find what works best for you and stick your meter in and get a reading. Now you know its, let’s say 1.5EC.

Next feeding you notice that your plant looks hungry and needs more food. So you increase to let’s say 1.7EC

The meter is allowing you to make measured and accurate adjustments to your nutrient strength, and repeat them between watering.

There will be a recommended EC or PPM for your nutrients if you arent already following it. That’s your baseline.

But back on topic, I’d see if the increase in peroxide strength makes a difference before going any further, then go from there.


+1 for using pool shock. I add it every time I mix a rez up and I’ve had no trace of algae since it also allows the rez to run a little warmer. Chloride is also a micro nutrient thats beneficial for your plants :v:


I can’t thank y’all enough for the help. I never get the chance to talk about this with anyone, due to prohibition I’ve learned to fly under the radar. It’s good to talk with someone in the know.

Okay, for the hell of it I checked the ppm and ec of my tap water.
PPM = 131 & EC = 278.

My question is when I’m adding the pool shock I should be trying to hit my ppm to around 170?

I’m going to follow your advice and just try upping my H2o2 before adding ant pool shock.



That’s how I do it. I would expect to end up being somewhere around 6 grams in a 20 gal reservoir.

And yes it’s definitely nice having a place to talk about this stuff. We take privacy very seriously here so we can have that luxury :slight_smile:

Cheers and good luck!

Edit: pool shock takes some stirring and time to dissolve before you get an accurate reading. So take note of how many grams you put in to get to the desired ppm, that way next time you dont have to stir it until it dissolves, and can just sprinkle it into the water and leave it.


I live in the Pacific North West and algae is just everywhere - in the soil and water. I have had similar issues to your from my first hydro grow - the slime, sludge, and strand type growth in all colors.

That crap is hard as heck to kill once it gets established. Normal, safe, preventive levels of bleach, shock etc do nothing to it, and beneficial bacteria dont help either. It takes strong levels of bleach or copper to kill that crap. Levels way to strong for your plants to be happy.

If you have algae, the only solution is fanatic light proofing. I started like you did - with an open rez in a “shaded” spot under my work bench. Tons of algae, sludge etc. The I went to black Home Depot totes and kept the lids on most of the time - still had algae. Then I started wrapping the lid in aluminum foil and then covering the whole rez with a blanket - but I still had white fittings and tubing carrying the water and still had algae.

This time my rez is 100% light proof and all tubing and fittings are wrapped with aluminum foil anywhere even indirect light can reach. Im a week in with the new setup, and so far no algae.

I am pretty sure your white rex and filter bucket are breading algae like crazy. You need to fix that or you are wasting your time with small doses of pool shock or H2O2, etc.

The other thing you mentioned is your PH getting unstable - what exactly is your PH doing?

You may have a similar problem to my PH issues. It turns out that excessive or even just vigorous aeration can drive the PH up over a short time period. I think this effect is worse when you also have algae. The extra air helps feed the algae which may also drive the PH up.

@Northern_Loki just sent me this link to explain whats going on with my PH issues in my HPA and AAA setups.

Good luck!!

Oh - keep in mind that those BioBalls are called BIO for a reason. They are designed to allow extra surface area for bacteria to grow. They will help a ton with aeration, but at a cost in terms of breeding ground for bad crap.

I used to think you needed to go wild with aeration, but Im coming to realize thats not really the case. Too much aeration might even be worse than too little. Its actually fairly easy to get water to 100% DO levels. You dont really need to go crazy with air stones, or bio balls, There is not really any real benefit to doing that and the down sides more than out weight any slight increase you may get in DO.


As soon as my nutrient solution becomes cloudy and I notice clumps of algae the PH begins to rise rapidly. I can lower the PH to 5.5 and in a few hours it’s back up to 8.0 or so. I’ve taken your advice and removed the filter buck, it was ineffective and just created unnecessary work.



Perhaps your bio balls are harboring something you don’t want in there? If it’s possible, you could try bypassing them on the next res change and see if anything changes.

Edit: if you’re using the nutes above and hydrogen peroxide, then you’re going for a more ‘sterile’ solution, ie nothing alive in it.


Okay, quick update. Tuesday the 13th. I broke down the system and did a thorough cleaning and disinfecting. I filled the reservoir with 20 gallons of water, added the Pool Shock at 38 PPM and added 100 ml of H2o2 then added my nutrients and ph’d the solution to 5.7.

Also removed the filter bucket made sure the lid is tightly on the reservoir and no light reaching the reservoir.

I’ll let y’all know in a day or two how things are going. Thanks again for all the help.



No doubt, I removed the filter completely from the system.


Good call, I think between that and the shock you’ll be golden now.


Good to hear. I’m not familiar with these bio balls but larry and beacher made a good point. Not really a need for a filter anyways if you are draining to waste, IMO, but I would still run that pump just without the balls or whatever to agitate/flume the surface of the water.

Edit: what I usually do is rig my watering pump up in such a way that when it runs it also diverts some water back into the res to aerate it. That way it’s not running all the time.

If you are still using that white rez, its probably not light proof. You can test it easy - just hold a bright flashlight against the inside - with the lights OUT in the room - and see if you can see ANY light getting through the side. If there is any glow at all through the plastic, you’re still gonna grow algae.

Also, white PVC pipes and fittings must be covered with foil or painted with a heavy coating of black paint.

I wasnt kidding about the fanatical part :wink:

Keep an eye on your PH after you do an adjustment and with the aeration running. You may well see a rebound in the PH when you first adjust the PH to your desired level.

If your water is like mine, and is alkaline at all, the aeration alone will force the PH to go up in a fairly short time.

If this is happening, your only option is to reduce the aeration/agitation of your water. Its that aeration that is driving the CO2 out of solution and forcing the PH to go UP. The circulating pump, and especially airstones will both do the same thing as far as the CO2.

Look at that video I linked above. The PH goes up just from running some bubbles in the water. You can see it change color as you watch.

Your setup - top drip feed to waste - doesnt really need any “extra” aeration anyway.

The water dripping into the soil will very quickly go to 100% DO all on its own even if its starting at a low DO level.

The basic mechanism is the same no matter how you grow. Very thin layers of water will reach equilibrium, as far as dissolved O2, almost instantly when in contact with the air. Im talking very thin layers. Just a few microns thick. Im talking about the very thinnest top layer of the water in your rez, or the thin layer on an air bubble, or the thin layer on a bioball, or a free droplet of fog.

Thicker layers of water take much longer to reach 100% O2. The O2 mixes with the thin surface layer very very quickly, but it takes a long time for it to go deeper in a container of water. This is why surface layers of water in a lake or ocean can be hi in O2 while the deeper water is dead as far as O2. All types of aeration are just different ways to get more water surface area in contact with the air as fast as possible. This is why fluming is just as good a way to aerate as bubbles or water falls. Its all about exposing more water surface area to the air as fast as possible. Thats why bio balls etc work so well. They create a large surface that has a thin coat of water on it. That thin layer is the key. That and refreshing that thin layer with new water from the deeper parts of the rez that have less O2. Bubbles, fluming, water falls all do the same thing - bring up new water, spread it out in a THIN layer so it absorbs O2, then replace it with new water - rinse and repeat :slight_smile:

Dripping into soil works almost as well. That fat drop of water will quickly spread out into a thin layer covering the individual pieces of dirt, perlite, rockwool, or what ever you are using. As the water spreads out into a thin layer on the individual parts of the soil, it will reach 100% DO very very quickly. This is why its key to not have your soil packed down and why you add perlite, etc to it. That perlite, fabric pots, etc all work to keep the air in the soil. Thin layers of water + air = perfect O2 levels - with NO extra aeration needed.

Keep in mind too that you cannot get more O2 in the water than it wants to absorb. Extra bubbling, water falls, etc wont increase the O2 beyond 100% DO. The only way to get more than 100% is to raise the pressure of the air, or the partial pressure of the O2, or lower the water temp. However, any “extra” O2 you manage to force into the water will quickly leave dropping it back down to a max of 100%.

Normally extra aeration does no harm - unless you have alkaline water. If you do, then the PH will go up when ever you aerate. As I said before, algae just seems to make it worse, but my water straight from the tap - goes up in PH when ever I aerate. Adding nutes makes it worse because it increases the alkalinity.

Im limiting the circulation pump in my rez to 1 minute every 8 hours. The only reason Im even doing that is to keep things stirred up so the nutes dont settle out. I also need to stir it because the surface will read a different PH than deeper down after the water sits for a while. The PH of the surface water will read higher than from deep in the rez. I stir it so I can read the PH more accurately.

Good luck!!


Hey just wanted to let y’all know how things have progressed with my reservoir situation. As I mentioned earlier I had done a reservoir clean out on the 13th. My wife who has Multiple Sclerosis became very ill and was admitted to the hospital on the 14th. So other than mad dashes home to top off the reservoir I haven’t been able to do much more than that. I was able to bring my wife home on the 21st so that evening I was able to really get caught up, after doing a trichome check I realized I’d be harvesting in four or five days so I emptied the reservoir to get it set-up for a few days of flush. I’m happy to announce that following everyone’s advice, pool shock, keeping the reservoir out of the light, which wasn’t difficult because the reservoir is outside of the grow tents and inside a dark closet I had almost no sludge the nutrient solution clear and stable. I couldn’t be more pleased, so thanks to everyone for the help.

I think for the first drain to waste grow using coir I did pretty good. I’ll know more when I harvest. I learned some things too and that’s always important. Next grow I’ll be sure to grow the same cultivars. I had three different cultivars (all autoflowers) two Rhino Ryders, one G14 (love the G14) and one Strawberry Nugget, the Rhino Ryders must be light feeders because I had some slight nutrient burn, but still looks they will produce well. Okay, again thanks for all the Solid Advice!



Wooohoooo @October_King enjoy your harvest you’ve earned it. Hope your wife has a fast recovery, sending some good vibes your way!

When things settle down don’t be a stranger and stop in and let us know how things are going!